Feeling Down

I'm 17 weeks pregnant with twins and trying to cope with the fact my relationship isn't working out, and I will have to do this on my own. My boyfriend has totally changed. He doesn't treat me the same. I can't stand the hot and cold anymore. I thought I was supposed to be the one with the mood swings. He was supportive during pregnancy at first but not now. I don't know if because of his work schedule or just his feelings changed. He is a good guy and i wish things could work, but don't want to stay together just for kids.