I'm overwhelmed and need advise

Hi everyone,
Needless to say, I'm new to this forum. I'm hoping to get an outsiders perspective of my situation. I've been married for 15 years. It's a second marriage for both my husband and I. We came from bad marriages, where we were cheated on, so it made our bond strong right off the bat, because of what we've been through. Over the years, my husband (who is ex military), has shown that he has a bit of a temper. He's never laid a hand on me, but he does raise his voice to me a lot and he knows that my ex would not only scream at me, but would always follow that up with a smack, or backhand across the face. So when Roman raises his voice to me, I break down, not just because he's doing that, but because he knows what I went through. The romance has dwindled over the last few years and its not on my part. He works crazy hours and I know he's tired, but he also is addicted to a game he plays on his iPad and recently, he has joined a group chat with the people he plays with. His phone is always beeping, that he has a message. That stupid thing goes off, both day and night and he told me right away, its from the game folks that are located all over the world. Because I work from home, I saw his iPad lighting up like the 4th of July with new messages, so I was reading some of them and it seems that my husband has been flirting quite a bit with a couple of the women that play the game. He calls them sweetie and they've all exchanged pics of themselves and talk about how fun it would be to meet up in San Diego for a beach party. I told him I read all the messages and the flirting really hurt me and how can he do that to me. He lied right away and said it was no big deal and I was looking for something that wasn't there and he would stop it right away and drop from that group chat. Fast forward two weeks and once again the beeping was back in high gear and I looked at the messages and not only did he not drop out of the group, but he went right back to flirting with the two women and sending more pics of himself to them. He seems to have one lady in particular that he talks with the most and she sends him pics of herself and has little pet names for him and also sends him pics of her shoes that she wore to work that day. They talk about things that one would normally talk about with their spouse and how their day is going and what they're going to do that night. I confronted him on it and he never even apologized. He just deflects and says why bother, because I'll probably leave him anyway and that I've always been looking for a smoking gun, so I can kick him out. He said he'll go to a counselor if I wanted him to and once again, he said he'd drop from the group chat, but I'm heartbroken and hurt that he's doing this and then lying about it, but also, that he's not even trying to apologize. I feel that if I hadn't have caught him in all this, the exchanging of phone numbers would have come next and then who knows what. I don't know what to do. Am I making too much out of this?