in need of advice

My boyfriend and I have been together over 1 now. We known each other for 3 years now. Just last year he cheated on me and I confronted him about it. He told me he felt sorry and I told him why did he do what he did? He said bc of our circumstances back then my parents didn't know I was dating him for he is older than me. We saw each other secretly when ever we could. He said he did it bc he taught I was playing with him bc I was young. I looked him at him and I saw he was crying he told me he felt sorry but he couldn't take back what he did. Which was he was messaging his ex and a girl who he eventually invited her to his house and she agreed. Which later she told her friend who was also mine friend. I forgave him tht time bc I truely loved him. I never loved somebody as much as did towards him.
Eventually we moved in together and just today he left his phone and I look through it and found he had been talking to girls behind my back. I really did trust him but now i know i was stupid to take him back
Now I dnt know wat to do bc after all I still loved him. I can't belief this is happening he seemed so sincere whenever he would kissed me and tell me he loved me
Please give me some advice! I know you all have seen many posts like this and think that I'm stupid to take him back which if it was my friend I would tell her to leave him but it's so hard doing tht