annoyed and over it

i am 21, my boyfriend is 28. we've known each other for 7 years but only "officially dating" for roughly 6 months. he's so sweet and makes sure i know he loves me. he cooks and takes care of me, as i do for him. but i just can't help but have this suspicion that he still talks to another girl. i know he never sees her in person because we are together 24/7, but i know he still talks to her and won't admit it. i feel he thinks i just won't leave him but honestly, i'm too young to deal with these games.