Is my husband cheating?

I don't want to be "the one in denial" so I'd like to get some opinions from the forum. I don't think my husband has physically cheated yet but I feel like he's emotionally invested in another woman and puts her first. He has very few friends and has never had many friends since we married 15 years ago. He's a bit socially awkward and has a hard time clicking with people which is the polar opposite to me. We got married quickly so this is a huge incompatibility that I didn't recognize at the time. I still love him 15 years on. He works with this married woman (they are both teachers). I know her and occasionally we go out as couples. I don't think her marriage is very happy. Her husband is a recovering alcoholic who falls off the wagon periodically and he's very loud and crass which is off putting to a lot of people. He's pretty much the opposite of my husband. Anyway, they have become very close friends and at first I was really happy about it. He needs friends and she also helped him be better at his job. He was on the brink of failing in his profession but she helped him as she's very good at what she does and now he's better for it. They now try to go out every Friday night for happy hour for a couple of hours. He invites me but knows I can't go because I work much later than he does and don't get off in time to be there. He knows it's a "safe" invite as I can't be there. Occasionally others will join them but more often it's just the two of them. They have even started going more than once a week recently. We've argued a lot about the intensity of the friendship for the last two years (there were times when they would exchange 150 - 200 text messages a day). Ive read most of them and they do appear to be innocent enough. Mostly stuff about work but I do notice a pattern of her seeking validation from my husband. Saying things like she's fat (she's not) looking for him to compliment her and stuff like that. My view is a woman should seek validation from her own husband, not someone else's. There have been two instances where we've had huge fights about the texting and then their entire text history is deleted from his phone. I suspect he confides in her that we fight about this and the deleted messages were him telling her I'm upset about it again as I've asked him to never tell her that I get upset over their friendship so he deletes it to hide it from me. The most recent issue was this weekend. On Friday they finished school. The last day is teachers packing up and checking out. I was invited to happy hour and actually had the day off so I could go but didn't fully commit as I had some things to do. I found out that her husband helped her pack up her room all day and was at the school but she didn't invite him along. I had texted him to see if he was going and he told me he had not been invited. I then found out my husband had told her I would not be going either and that is why she didn't invite her husband. It was going to be just the two of them. As luck would have it the battery in my husbands car died so we dealt with that and he couldn't go to happy hour with her. We had fought a little about her not inviting her husband and how weird that was earlier in the afternoon so when the battery blew I made a comment that is was meant to be and was sending a message. We got into a bit of an argument about it again then went to dinner. I again told him it makes me uncomfortable that they were going to go to happy hour excluding her husband and that he had told her I wouldn't go anyway and that I just felt their relationship has crossed into an inappropriate place (we've had that discussion many times). He kept telling me nothing was going on and it was messed up that I don't trust him and that she was the only friend he had and I'd be happier if he just sat home with no friends. I told him that guilting me over a relationship that made me very uncomfortable was adding to my hurt. I told him I didn't expect him to not be friends with her but it needed to be appropriate. We could still do stuff as couples and he can have happy hour sometimes but it feels like they're now trying to do it several times a week and they are more happy if it's just the two of them. There is a third lady who goes sometimes but she bails more often than not. After all of that conversation he tells me he wants to go check a store out quickly. I tell him I'll wait in the car. Suddenly, I get a text from him asking if I want to go to their hang out place the following Friday. It was meant for her. And they have never done happy hour over summer break before so now they're making plans during summer time which is new. I looked at his phone when he got in the car (I was furious that after we just had a huge fight about it and I had even said I was glad it was summer so he'd take a break from her he would text her within minutes to set up another time to meet). He had also told her he was so sorry that he couldn't make it tonight and put a sad face emoji. The other thing that gets me upset is that when she texts she expects an immediate response. If he doesn't respond immediately she just keeps texting asking if he's ignoring her, etc. It's very odd behavior for just a friend but he doesn't think it's a problem. He will also ask me if I said anything to upset her when we get together. I never have but he's overly concerned with how she feels. He gets anxious if he can't text her right back as she'll think he doesn't like her. She's very needy and he seems to feel that he has to meet her need for immediate responses. Even when we're out together doing something. While most of their messages are about people at work there is a fair amount of banter that sees them validating each other. Her saying she's fat. Him saying he's stupid and them each telling the other they are not those things. Anyway, on Friday night - after all this happy hour stuff went down we had a really big dramatic argument. We talked divorce seriously and he slept on the couch (we don't do that normally). The next morning he told me he loved me and didn't want to divorce and wanted to make our marriage work. I told him I did too but things had to change. He then cried while he hugged me (he rarely cries - like hardly ever). The only problem is he wasn't crying about our near divorce - he was crying over the thought of not being able to be friends with her. Am I completely stupid to think this is not a physical situation? I feel like he's emotionally cheating on me which is not acceptable. I'm going to go to a counsellor to get some guidance on what I want to do (he has refused counseling). But does this behavior suggest more is going on? I would never have thought he would do that - he has no game to be honest, but I definitely feel like her feelings are more important to him than mine. I make a lot more money than he does and we have a certain lifestyle that he enjoys. He denies that this is why he stays but a very big part of me thinks he's with me more for the financial benefits and he gets his emotional needs met from her. He doesn't fully disclose his real self to her. He's a compulsive video gamer and she has made it known that she hates video games so he's forbidden any mention of video games to anyone he works with to avoid her finding out. When I ask him why it matters what she thinks of his gaming he gets defensive and says he doesn't want her to know. Any thoughts would be appreciated. I've contemplated hiring a PI to watch them at happy hour one day but part of me says if I need to do that I should leave. I'm so lost about what to do. I don't want to give up on my marriage if I'm making more of this than I should - but I don't want to be a fool either.