I dont know what to do?

i like this boy, and i've like him for a WHILE in fact (being the retard that i am) i helped him start dating his NEW gf whom he is deeply in love with i think. i cant help but like him and even as i started getting them together it was kinda a mechanism to hide the fact that i was infatuated with him, now he flirts with me but i know its innocent, i dont know what do to because even though me and his gf arent close friends i feel bad, but at the same time when he JUST alks to me i get CRAZY erflies. give me advice and pointers PLEASE.