namechanged I'm so for you.
it sounds to me that it's not so much that you don't want this baby but that you're terrified of what it will mean for you and how you'll cope.
I agree with everyone else about getting counselling. Ante-natal depression, as Lizzylou says, is very common, almost as common as PND apparently, but much less diagnosed. Like PND it is treatable. You just need to ask for help. Once you're getting treatments, and you're able to get to the bottom of why you're so scared of having another baby (it may not be what you think it is), you may find that suddenly you want this baby very much indeed. It is absolutely your right to choose and if you choose to have an abortion because it's the right thing for you, that's fine. But if you make the wrong choice because you're depressed and scared, it could be something that you never get over. Counselling will help you realise what's really right for you.
FWIW, your husband sounds as though he would bear with you. It wouldn't be easy for him, I'm sure, and he may harbour some resentment issues that he may need counselling for himself, but if he's already reached the stage where he puts your needs first and has said he will support your choice, then it sounds to me like he's a decent guy who will be there for you.
Lastly, please don't think that one horrific childbirth experience condemns you to a second. My Dsis had an awful labour with her first and was terrified about her second, but because she's had a lot of chats with her midwife and drawn up a good birthplan stating what she wanted if there were complications, her labour was relatively easy the second time around. It's well documented that very difficult labours can indeed affect the bonding process between mother and baby. It doesn't mean that history has to repeat itself. Forewarned is forearmed. Having had this happen to you once, you can take many positive steps to minimise the risk of it happening again.
Good luck. I hope you get the support you need and make the right choice for you.