Pregnant and feeling unwanted

I've been with my partner for just over three years and i'm 11 weeks pregannt. I already have a 3 year old son from a previous relationship. When me and my partner first got together he made me feel so special and he treats my son as his own. After about a year of us being together, he started to let me down, e.g. I wouldn't hear from him for a week. Over the last two years he's managed to spoil a holiday abroad, my engagement night and the day I told him I was pregnant. He's tried various prescribed tablets for his 'moods' and nastiness which he says he inherited from his father. His mother agrees and when we've been having problems, she has told me she wouldn't wish the life she had with his father on me. Anyway, for the last two years, he only seems interested in sex every so often and this hurts me so much. I feel so unattractive like he doesn't want to touch me in that way and it really hurts. I've become so insecure about us, and everytime I try to explain why i'm so insecure he tells me it's all in my head and i'm pathetic. I really don't know what to do as all we do lately is argue and i'm terrified what the future will be like.