I can honestly say I feel for you. Like Roly I have a lot of chronic medical problems and it takes a lot for someone to be involved with me. I'm currently only with my husband, but even for his relationships it has to be considered. They have to know that if I can't move, or am in the hospital, dates will be broken as he will be with me.
That being said, if his g/f needs him, at no time have I said no I'm more important. There was a night a few weeks ago that she needed him and I was in horrific pain. He has NEVER left me when I have hurt that bad, but I knew he needed to go to her. I asked him to get what I may need while he was gone-water, snacks, medication,etc. and let him go.
Honestly if she were in the hospital. we'd probably both be there, and I don't really like being around her at the moment. But she is a part of my husbands life. Part of what makes him happy. I owe her for that.
Granted she lives 30min from us and we don't have kids to take into account, but we go home to ohio quite a bit and that is a 6hr drive. I've done some thinking on it, after reading your posts and honestly if she were hospitalized for unknown reasons, we'd head back here so he could be with her.
The fact that he didn't even ask just blows my mind. If I were dating someone, I'd want both of them with me if I were in the hospital, esp if they didn't know what was wrong!! We seek out relationships to fulfill needs. And one of those needs is to be taken care of. To have someone we depend on there, even just to hold our hand.
Granted , I don't know your whole situation, but I have to agree with those saying it sounds like you are a second thought to him. That just isn't right in my book.