Still have feelings for my pregnant ex

So we split up around 5 weeks ago she's 21weeks pregnant. I still have a lot of time for her and my feelings are still there too and I know she feels the same. We see her a few times a week and I plan on taking her for lunch this weekend the thing is she is so up and down at the moment. Is this a pregnancy thing? One day she will talk like she hates me and the next like she loves me. I know deep down she still has feelings for me... It's just I don't why she gets like this. I left her as wasn't getting on well living together with our 3 children from previous relationships.  Should I give us a other shot?