Boyfriend help...?

ok so i started dating this guy thats older than me by 1 year so i dont realli kno whats going on in his life, i see him near girls a lot and once i saw him walkin with som girl and hanging out wit her and he teaches her how to skate. i also heard him talkin on the phone w/ a girl and he was askin her to come somewhere with him... should i be alarmed? could he be cheatin on me? (ps. he always tells me im beautiful and that he loves me and me only and that im te only one in his life, and that he's had lots of girls but never anyone as good as me)