Struggling with 3.5 year old

I feel absolutely terrible writing this. My son is the absolute love of my life. We recently welcomed another little boy into our lives about seven weeks ago. Unfortunately and terrifying so about two weeks after our second son was born our second son developed sepsis. it was touch and go and we were in hospital for five days praying to God that he would be okay and that we could get him home. Thankfully we are home now. Little boy is settling in brilliantly with his big brother however eldest is being more than tricky to put it mildly. Just before our youngest came along, our toddler started acting up far more than usual. We’re talking constant screams constant fights and constantly been screamed at no . He does have a slight issue with his Speech which is definitely delayed. He says words but cannot take direction in any way shape or form and the A word has been brought up once or twice at nursery. He throws things, he hits, screams and quite frankly he just seems to hate both his parents. I have been having to stay at home consistently in the last month or so to shield our newborn from any other nasties to protect him and as a result dad has been stepping up to the plate with Nursery Runs et cetera. I know that this is coming from a place that he feels as though he has lost me in some way while I am desperately trying to spread myself out between the two boys but find myself having to give myself more to my youngest than I can my toddler and find myself getting exceptionally frustrated with the toddler. Please can someone just tell me if this behaviour is normal or if I should be getting him to a behaviour therapist. As I say his outburst are becoming violent, I can’t get him to take any direction and he just screams at me any time I talk to him. He literally seems to hate me and I don’t know where my sweet little boy is. Thanks