Behavior issues at school

My son is 4 and is having behavioral issues at school it’s like a switch in his head isnt working correctly. He knows right from wrong. He knows how to act. We have now had 3 meetings with the school about it and they feel the same way I do about the school thing. Me and his teacher have takes about it so much as well. I’ve tried getting a referral from his doctor to be seen and she just wouldn’t. She is now no longer with the office we go to and I’m waiting on a call back from the new doctor he will be going to. I feel like a failure that I haven’t been able to help him and my husband is normally so supportive and helpful but for this thing it’s like he’s pushing all the blame on me and I just want to cry because I don’t know how to help my child. Currently pregnant with my second so not sure if thats also playing a part in how I’m feeling. The behavior was happening before I even got pregnant so we know it’s not because of that. I’ve talked to my bestfriend about it too but she isn’t really helping at all kinds being like she isn’t the parent and doesn’t know and I get that I do but also I don’t need her to have answers I just need her support. My son is sweet and so smart and helpful and then goes to school and throws toys and hits others like I have no idea why he’s acting that way as well and we have tried everything we can think of. The teachers and staff ask him why and he says it’s funny and because of his memories ( no idea where he gets the memories part ) he will tell you it’s wrong and he won’t do it again but then he does. He’s only acting this way at school. I’m hoping the new doctor will finally help him. End of my rant I guess it you made it this far any advice would be amazing.