The behavior of the 3 year old child

Ok I need advice I'm pregnant with me and my partners second child we l have been together for 3 going on 4 years our daughter is 1 and I'm like a month or so pregnant,... anyway we have a " friend " it's a guy who swears he's straight but he acts like he wants my partner and I'm getting really insecure because we have talked to him about it and he doesn't change his behavior and it's casing stress for me and my partner

I'm a first time mother to a 2 year old. His behavior suddenly changed, he's defiant, he destroys things (like pulling things off wall, like the trim and wallpaper), he throws things to break them. He is aggressive towards me and constantly tries to hit me. He has meltdowns for sometimes hours on end, he bangs his head off the floor and tries to hurt himself. I'm feeling so defeated as a mom because I don't know what to do or how to discipline him. I feel like it just gets worse and worse each day. I love him so much and it hurts me that he acts this way. I feel like I'm doing everything wrong. Other people complain about his behavior . This is on a daily basis. It's affecting my mental health. He doesn't want to be independent at all. His communication is getting better but he still isn't fully talking yet. If anyone could give me some advice on how I could help change his behavior or at least correct it would be greatly appreciated.

does anyone have a 3 year old that has behavior issues? trying to see if anyone has the problems I do.

Is it normal for a 3 year old boy to be pinching cause doctor told me he might have autism and q specialist tested him and said yes to his behavior but he now bite his brother how do I stop him from biting