Hi Tia
Firstly, don't be so hard on yourself. With every good will in the world, things don't always go to plan. However we can adapt ourselves to any given situation, so secondly don't despair.
Does your recent partner know that you are pregnant?
Just because you are no longer together, its not a given that he won't be interested in his child. OK, if he does know, he might be slightly bricking it, but once he's over the shock, he might have a different view on things.
Does he have a mum and dad that he has a relationship with, if so they will be grandparents eventually and they may well be delighted (obviously I don't know any of your back-story so I am just surmising at this stage. You mentioned that you were together 2-years and were planning to get married, so it was a pretty established relationship even though its not worked out, it doesn't necessarily mean you can't co-parent. Again, I know nothing of your story so I'm just making suggestions based on what you've written.
Does your ex have siblings that you have developed relationships with during the time of your relationship with your ex?
Being a single mum IS hard, I know I've been there and chosen to be single for the last 12 years as for me I haven't wanted to get involved with anyone, and to be honest I found juggling a child enough without having to juggle a relationship as well - but that is just my preference.
Maybe share a little more information and then I can try and advise further based on that?