I'm in almost exactly the same boat as you, OP. Had a termination 2 years ago, have been desperately sad about it since and always said I could never do it again. Accidentally fell pregnant by boyfriend who I was pretty much already broken up with (it was "that night" at the end of a relationship where you get hammered together and reminisce and cry and shout and wish things could be different but know they can't).
He is absolutely devastated and wants me to have an abortion but I just can't, despite about 49% of me thinking it's probably the right thing to do. I'm nearly 33 and worried that this may be my last chance, esp as I don't ovulate regularly already, and I am far too devastated at losing him (the break up was all on his part and there is OW) to even consider being involved with someone else any time soon). He has said all those same things, "why do you want this, it's not fair on the baby, etc etc" but he is just trying to play on my fears and manipulate me, and I'm not having it. I have had many sleepless nights worrying if I'm making a huge mistake, if I should have an abortion and just be rid of him out of my life rather than tying myself to him forever, if this means I will be single forever, if it is the end of my career, if my child will hate me for always having to be the one to instill discipline etc. but I have concluded that I am strong enough and that this is the right thing for me, as scary as it is.
I am now 12+2 and I think he is starting to accept that this is happening and that at some point he will have to make a decision to be involved or just get out of my life completely- I have given him the choice.
I'm sorry I don't have any advice, really, other than to seriously consider all your options but don't be afraid to stick to your guns. Don't be too proud to take anything from him either- declining hold support, for example, won't give you the right to deny him access should he change his mind and decide he wants it. I just wanted to let you know you are not alone in this situation, there are more of us!
We can do this- plenty of people have done so before us and plenty of people will do so after us. Keep your head up