Firstly, congratulations! Your pregnancy is wonderful news and please don't feel guilty for agreeing. You deserve to enjoy this time in your life without a miserable cretin putting a negative spin on it.
I was pressured into having a termination four years ago by my partner at the time, and honestly, there isn't a day that goes by where I don't feel haunted by it. The man who pressured me into it even had the audacity to grieve and sulk afterwards, telling people how it was MY decision in an attempt to alleviate his guilt. Ugh. It angers me just thinking about it...
Anyway, I'm currently 36+3 weeks pregnant with my DS, and I've approached this pregnancy differently. I've not allowed anyone's misery or negativity to get me down or sway my decisions. Everything I do is for my baby.
My current partner has been negative, like yours, since day one. He initially accused me of ruining his life and of being selfish and not giving him a say. We've been together for 3 years, we tried for this baby. and we've been solid as a rock, so I didn't see this coming either. C'est le vie...
I'm putting his bad attitude down to nervousness, because it's mainly fleeting. I've been told that men don't feel the same connections as us women during pregnancy, which makes sense. As such, I've tried to get him physically involved, by doing small things like getting him to rub moisturiser over my bump, etc. Sometimes it helps. Sometimes he even smiles when I put his hand on my bump where my DS is kicking. Sometimes, however, he's still a miserable bastard about everything. But if he eventually walks away then so be it. My son will be my priority, and there IS help out there for single mothers if you need it.
Be strong!
Be happy! This is a wonderful time. Enjoy it. 