SOS I don't know what to do

Yulissa • I'm 19
Hi I'm new but I need help with this. So I have been dating my Current Boyfriend A (so we can keep him nameless he will be A)  for a few months but recently I have noticed that I'm not emotionally stuck in the relationship. I have started to feel suffocated and I don't want to hurt him he is very sensitive and super nice. I also notice I'm still in love with my ex (well call him B) and I was with him for a year until I found out he cheated on me by sending nudes to his ex while he was "drunk". I don't know what to do cause I have been in love with B for years. I'm talking 5years before he asked me out and I have loved him to the max my heart can take. I don't know if I should/how to breakup with A. I'm so confused.