I'm no expert, and I have no experience with late term abortion/loss but I do have experience of what you're going through. I have suffered from OCD for many many years, officially diagnosed at 14, have had many treatments including intense counselling, CBT etc. I found out I was pregnant, when I was 9 weeks pregnant. Just a few weeks after the biggest drinking, smoking weed and cigarettes bender you could possibly imagine. I was absolutely devastated to not only find out I was pregnant, but also that I had done that to my baby. I was also seriously considering terminating the pregnancy because I was terrified that id have to face a baby I had hurt by my stupid actions, even though I, like you didn't know I was pregnant. During this time, my OCD went crazy. I had a lot more intrusive thoughts, that if I didn't terminate the pregnancy, my child would be my karma, that it would be horribly disfigured etc that my DP would take one look at our baby if I continued and leave because surely I had damaged it beyond repair. I felt like my head wouldn't work anymore because the guilt was physically dragging me down. I left my job, because I couldn't function as a human while I had all this guilt..
One of the ways I have dealt with my OCD when its been 'peaking' is to set myself step by step goals. I tried to apply this in the situation and thought the only solution was to have a termination, I.e get rid of what I thought was the cause of my guilt, and then deal with the guilt and then it would be ok and I would just move on.
I tried to think 'practically'. And you know what? My DP begged me, even went so far as to say that all I had to do was have the baby and he would take it and I could walk away if I still felt the same. I agreed, because I didn't have the strength not too.
And you know what? Towards the very end, I think I was about 30 weeks gone, I suddenly realised that I hadn't thought about anything negative in regards to the pregnancy for a long time, and actually allowed myself to get excited. 
That baby is now my beautiful, perfect, little girl. The girl who makes everyday something to look forward to. She's my little sidekick, and her Daddy is my best friend and still my Partner.
I understand how terrified you are, I truly do. But you need to understand that you are a human, and a mother. We make mistakes, you have done NOTHING WRONG. You desperately wanted this baby, and he/she is coming. And when you set eyes on your perfect baby, everything else will just melt away.
Sorry for such a long post. I'm not great at getting across what I mean! 