Hi, sorry to hear you're going through this. I think that sometimes pregnancy hormones can transform someone into a completely different person.
My situation with my OH is a little different from your situation with your girlfriend. For a start, he wasn't very supportive at the beginning of my pregnancy. However, all I wanted to do was push him away and not have anything to do with him. I couldn't stand the thought of being with him and every single thing he did annoyed me completely.
After a while I realised that I really did need him and love him and want to be with him. When the whole shock of being pregnant died down I guess I was a little bit clingy because pregnancy can make people feel so vulnerable. I went completely the opposite way for a while.
It's very scary to think that your body will be changing and that you have to push a baby out at the end of the nine months- a baby who will completely transform both of your lives! It terrifies me even now just thinking about what sort of parent I'm going to be, so hormones and a mixture of these thoughts is enough to send anyone loopy.
My best advice would be to give her some space. Perhaps send her a text saying that you're sorry for annoying/upsetting her and that you'll give her a bit of space until she wants to talk to you again. She probably feels quite pressured and trapped.
I honestly don't think you've done anything wrong (and you seem like a very sweet guy) but it might be worth sending a text along those lines just so she knows that she has space to think. Personally, I think the whole blocking you on fb thing is completely unreasonable but I know how awful those hormones can be.
She'll probably gradually become more reasonable as her hormones begin to settle down. I wouldn't expect an overnight change, although having said that, it can happen for some people. I wish you the best of luck and hope things get better between you and her.