Was he emotionally cheating on me?

I have been with my fiancé for over 3 years. We currently just rented our own house. I thought everything was going great until he received a text from our girl friend at the beginning of the month. She told him her fiancé was talking to other girls online sexually. Then eventually, she told my fiancé that hers was abusing her physically and sexually. She told my fiancé not to do anything about it considering he was best friends with the guy. That's how we all became friends.

She continued to text him, telling him everything her fiancé did to her in detail. For some reason, my gut told me she was making the whole thing up but I never said anything. We continued to hang out with them as normal. She kept texting my fiancé all the time. I was starting to get jealous and even told him. He said I had nothing to worry about. That she was like a sister to him. He even let me read their texts early on but then stopped letting me read them, saying it was weird. I then felt something was going on but he promised me nothing was

We were over at their house a few nights ago. This is when everything went down. Her and her fiancé ended up getting into an argument about something and she ended up taking off. He told us it was best if we left. So we headed outside, when he stopped my fiancé and called him over to talk. I was out of hearing range so I had no idea what they were talking about.

After like 20 ,minutes, she comes back home and is talking to her fiancé while I am sitting in our truck. My fiancé comes over and sits with me, letting them talk. He then finally said he had to tell me something. He said that over the past couple of days, he had been flirting with her. He said you wanna know why? Because she actually listens. I was hurt. Hurt because he was flirting with her and because I gave him the reason to do it. I don't really listen that well to him when he is telling me his feelings. I always get mad at him for everything. I freaked out, got out of his truck, and started walking away to head home to get my things and go up to my parents house.

He followed along side the road, telling me to let him give me a ride and that he was sorry. He was crying and everything. I am stubborn so i didn't get in the truck with him. Our friend and her fiancé start to follow me in their car too. She got out to tell me that nothing happened between them. But I was so angry, I just ignored her. I believe her though. I don't think he would physically cheat on me.

I'm not gonna go on with the rest of the night besides the fact that I ended up at home with him but didn't fall asleep until 7 the next morning when I had work at 2pm.

I just feel so horrible. I'm paranoid whenever he's on his phone. I've been crying a lot lately and then I'm fine the next. I just don't know what to do. I love him and don't think I could leave him but she wants us to be friends again after all that happened. I haven't talked about it with my fiancé about being friends with them again but I know he will continue being friends with them.