hello,
aww bless you are in a siuatoin arent you!
no offence but its a bit harsh the way you say you were happy when she was going to "get rid of it" its a baby and despite the circumstances between you and her the baby should be given a fair chance. ( sorry )
anyway i do feel for you, i certainly know for a fact i couldnt do it, if my partner got someone else pregnant while we were on a break or split up and then we got back together i couldnt do it, i would resent the child! i know that makes me sound like a cow but im being honest, you have to be fair to the child, if you think you would resent the child dont get back with her, me and my partner have a little girl and a baby on the way, he has a older daughter from a previous relationship 2 years before i met him and i find it hard and always have to bond with her, so i know i couldnt do it if it happened while i was with him. but thats my fault and would be up to me to be the bigger person and say no i cant do it,
its up to you, its your desicion to make whether you stay or go, if she keeps the baby you have to be 100% sure you can do it, seriously or it will drive you mad for years and its not fair for her the baby and certainly not fair for you as you arent the one that caused all this.
good luck, hope all works out for you x