My personal advice is that secrets do more damage than truth. We can get strength from truth and when we "know we've won." Compassion and understanding of others trials are what we should all strive toward. It helps release us from our own burdens and focus our energies in positive directions. I believe it is ultimately "selfish" to keep things hidden that may be of "help" to others. We are not impositions on one another when we are of good intent. God Bless.
I'm thinking along the same lines as mermaid. Have you ever thought if you talk to your gf about your health issues, she might be more willing to share more of hers with you? Sometimes it's easier to talk to someone who's been there, and knows what it's like to go through the pain and agony of waiting to know something about a serious medical issue. If you don't tell her and she somehow finds out later, what do you say to her then? Sure, you can tell her you didn't want to "burden" her, but I really think this could be a talking point for you two that could possibly bring you closer together. I am sending positive thoughts to you both, and will keep you in my prayers. I really hope you both get the best outcome possible! A good relationship is worth the work it takes to maintain it. Best of luck to you.
Gail :)