How do I trust and let go? 10 points for best answer?

I'm in a new relationship. And I have a lot of trust issues and other problems related to self esteem. She still talks to her ex's and I find myself being worried that she still wants them. We are also fighting alot lately. She has to have another back surgrey, which could leave her paralyzed in a few weeks, and she is taking out her fear on me. She's been in alot of pain and she's scared and instead of dealing with it she snaps at me alot and here lately it seems like she is constantly ill tempered. I don't know how to handle this situation. I've never been in a relationship before were someone still talks to their ex's and has a chronic health condition. I just want to be there for her and support her but it seems like I can't do anything right. I always seem to do or say something that upsets her. Any advice would be great.