By boyfriend and I have been dating for 5 months. Today I found out, a little while ago early in our relationship he was texting my friend flirty comments. She never wanted to tell me about it but has always said she hated him. I demanded her to give me a reason to this and so she told me what had happened.
I approached him about it and he say it's something he truly regrets. I know he has a very flirty personality and since he has changed it for me since he knows it bothers me. I want to forgive him but I have trouble trusting him. He means so much to me and I know he would do anything he could possibly do to make me happy.
The thing is if he had the nerve to be doing this with my best friend how can I trust that he doesn't do it with other girls. Although this was done a while ago and I know our relationship was still a new thing, I thought he has put his past behind him or the best.

It would be helpful if I can get any opinions on this. I want to hear everything people have to say. All is appreciated. Thanks :)