Advice!!

So me and my bf of 2 years just had a baby 2 months ago and ever since I had him I’ve been severely depressed, irritable and felt the need to isolate and do everything myself and I sometimes get mad at him for doing something or mad for not doing something. I feel like he isn’t enough and I deserve better and I feel the need to cheat bc I cannot live without him (we have argued a lot and he’s left but I always beg for him back) I have cheated on him and I know I have a problem and I’m fucked up but idk how this is going to work bc we can’t leave each bc of our son and we both refuse to let go and I feel like he deserves better as well someone please help!!