So I like this girl a lot for the past 4-5 months, she is a very good friend but she already has a boyfriend so I never told her, recently she told me that she had a crush on me before she knew me, now I feel that I should also tell her my feelings ?
I don't know if she is happy in her relationship but she's been dating for almost an year now.
What should I do.

Tell her that you have feelings for her, but you understand that she is in a relationship and you don't want to act on your feelings out of respect. This will let her know that she can come to you if her present relationship fails, and that you are a nice guy.

She h a d a crush on you b e f o r e she knew you and now she has a boyfriend.

You should do nothing.
She's with somebody else;she's off limits.

Dude put yourself on the other guy shoes. Would you like some one else coming to your girl telling her he likes her? I bet you won't. So respect that and like amicon said "you should do nothing"

You better be very careful here guy and truthfully, let her know you're friends, but will be a rebound to no one, and going behind her b/f's back shopping for another guy to have, is not what you are about, as tempting as that idea may be.

If you pay attention, you might be learning something about your friend that you didn't know, but need too. If she isn't happy with her boyfriend, why should you be her emotional tampon at the risk of your dignity and self respect.

Look I know you may want a chance with her, but you would feel bad losing a girl friend, and a friend, because of her personal issues. So instead of telling her of your deep feelings, ask her what's wrong with her relationship with her boyfriend. I suspect they may have a problem, so get the facts of why she would be fishing about your feelings for her, before you go confessing your desires for her.

She may not even have that kind of crush to leave her guy for, she may simply be expressing feelings she had, so respect her relationship and don't undermine it, or your friendship with any confessions.

Play this really cool. Do NOTHING, let her talk, and pay attention.

Thanks for your responses
But I really really like her and I have a gut feeling she still likes me too ( I know she has a boyfriend but isn't it possible? The way she talks and looks at me ) , I mean this is a girl I've been thinking about for the past 5-6 months,we have a lot in common,. and now she comes up and says she had a crush on me, shall I let it pass and maybe regret the rest of my life thinking what could've happened had I told her? Or shall I tell her and risk losing a friend ?

What do you expect? She dump her boyfriend for you? Isn't that cheating? Wouldn't you worry if she would do the same thing to you that you want her to do to her boyfriend?

No, the decision is obviously hers, but shouldn't I at least make the feeling clear from my side, and see what happens ? Instead of staying back and regretting later? This is just so much confusion :/

No more answers ? :(

I am shocked you didn't say "What about your boyfriend?" when she came up to you and told you she has a crush. That's what most guys would do, since it's a big red flag when a female goes behind her boyfriends back, don't you think so?

What makes you think she wouldn't tell another guy she has a crush on them, if she was with you??

Are you seeing the point I am making?? Don't let your own feelings make you blind to simple reality guy, that's will hurt.