He has a girlfriend but i really like him?

i kinda like this boy, and he liked me ages ago, but i said no to him because this other boy had just asked me out. anyway, everytime he looks at me i get erflies, but he has a girlfriend hes been with for a few months now. she always gives me the evils, is a tart and doesnt really seem to be the type who would understand him. im probably saying all this out of jealousy, but my friends have noticed this too. anyway, ive recently started talking to him again, and hes started to complain about his gf and keeps asking me for my advice. i like him a lot, and want to tell him how i feel. should i?