Very tricky situation....

Hello everyone my name is Helena, i'm 22 and I'm new here... I'd like some of your time to tell me what you think about my 'tricky' situation. So here's the deal. There's this boy in my life that is into me for 15 years now... He's always been telling me how he feels about me and he always said he wanted to be with me but I never really gave him a chance even though I kinda liked him too. I can't really figure out why I didn't give him a try, something was just holding me back. A few days ago that I saw him again he still seemed very interested in me...like..very !! Plus he told me again, it wasn't plain flirting....It was love confession once again ! But......this time, the thing is he is in a relationship for over a year now. At first I thought I wouldn't do anything since a) I must have not given him a chance because maybe i'm not so into him and b) because of his girlfriend. However, I changed my mind, probably because the girlfriend situation got me intrigued. But still don't know whether I should do something with him... I mean I'm wondering if he wants something casual or if he has serious feelings for me as he always claimed he had. I fear that those feelings might have gone away now and he wants something casual, which is something i'm in no way interested in !!! Still, I can't believe that feelings of 15 years could have just gone away... I mean it's like a whole life ! What does he want in your opinion and what should I do ??

I don't think it is a good idea to pursue somebody already in a relationship. Somebody is going to get hurt and that is bad karma. What goes around comes around.