No judging please..

I have 3 kids my daughter is 4, my son is 2 & my new daughter is 9 days old. My son is so bad that no one likes being around him & it makes it hard for me to even enjoy my days anymore much less waking up in the mornings. I’ve been to his doctor, I’ve done everything & nothing works. When he does something bad he immediately apologizes for it because HE KNOWS what he’s doing is wrong. My 2 oldest children hasn’t seen their biological dad in almost 2 years. The guy I’m with now is 42 & I’m 23, he told me the other day “if your son wasn’t yours he wouldn’t be aloud back at my house anymore” & he also said “I’m not going to lie sometimes I’ve thought about giving up on us due to the way he acts” he’s tried helping me with him & nothing works. I dread picking my own kid up from the one sitter that will bother watching him when I need her. Everyone has told me they have never been around a 2 year old as bad as mine & it’s making my life hard. It’s making me depressed, it’s making me feel like a failure & a bad mom for thinking this way about my own kid but idk what else to do. Please send advice.