Why is my husband so nasty?

we have been married for 18months but together for 4years. I have insercurity problem which do stop us doing alot and cause ALOT of arguements. My husband wanted me to get professional help as it ruining our relationship so i have and that was 5 weeks ago. My husband has always either been very kind and loving about my problem or he will be the total opposite.. shouting screaming, not understanding and sometimes things get physica between usl. However, after we have both calmed down he always says i push him to get that angry and its all cuz of me and if i wasnt like i was then he wouldnt ever get angry. when he is angry he always says " i want a divorce i hate you" and his words really hurt me and normally i completly breakdown in floods of tears. He just leaves me crying all night and will go and sleep in a different room and just leave me to cry myself to sleep. since getting professional help things have got worse. i really thought he would be supportive and stand by my but instead he loses his patience more and more quickly and now this week he just keeps saying it over he hates me and wants a divorce he tells me to F off and leave him alone. im never allowed to really express my feelings, everything is always my fault and what i dont understand is that he has put up with how i am for 4 years and now when im getting help he can even support me. i cant focus on sorting my head out with the help im getting as im so upset at how nasty and cold he is with me. he was even looking up how to divorce your ex on the internet. i just find it all so immature and heartless. he said 3 days ago it was over he hated me etc then yesterday we were getting back on track and today just because i disagreed with something he said he flipped out and now its over again. i suggested he gets help for angry etc but he says there is nothing wrong with him if i didnt act how i do with my insercurites then he wouldnt get like he does. im really confused and dont know what to do.. i feel im the love sick puppy getting trampled on always apologising and i dont want it like this. any help would be great thank you