How do i stop worryin about my gf gettin attracted to other good lookin men n cheatin me??? m obsessed ,help?

m jus too insecure abt my gf,who is damn beautiful compared to my average looks...all the time i m obsessed wid thoughts about her gettin attrctd to other good lookn men ..i get a huge inferiority complez when sum hansum guy passes by..i jus go mad in my mind...evrytm i jus end up ruinin our conversation by askin.whom did she meet,wat did dat guy say...sumtimes even i foolishly ask..did u get attrctd to that person...i mn i knw dats foolish of me coz i knw even if she does get attrctd shez not gona speak it out for she knws i might not like it...m jus too worried n insecure abt her cheatin me...bt i duno i cnt either leave her..pls help