OK, I need Help.

My Ex-Girlfriend, whom I am still in touch with as a friend, was feeling very depressed today, so I spoke to her and asked her what is wrong. She said that she has a crush on someone. I asked jokingly if it was me, and she said very seriously that she couldn't tell me that. I carried on talking with her, asking about 'him' and she basically told me about the same circumstances we were in. I am now in very strong suspicion that it is me that she likes.
The problem lies in the fact that I have a girlfriend. The problems keep on coming though, She is being tortured internally by this, because she knows about my girlfriend (one of the things she described about this boy was his girlfriend who was a close friend of hers) and she dosen't want them to brake up just for her.
I have no intention of breaking up with my girlfriend, but I also do not want my Ex- to suffer what she's going through.
This is all asuming of course that it IS me she was talking about.
I don't know what do do next. Help me, how should I find out whether or not it is me? If not, how can I help her in her predicament, if so, Can someone tell me a way of sparing her feelings, staying with my girlfriend and still keeping my girlfriend and my Ex- as friends?