Boy friend advice.......?

Okay so i have this boyfriend that sort of has a profile of dating them macking them and then dumping them after a week or so. His longest relationship is 1 year. and he says he isent using me just to mack him. and its been almost a week and he hasent asked for anything, which is pretty good for him. I really think he likes me. but then he was txting this girl and he acsedently sent my bestfriend the message instead of her.. and the message said "whats the dirtiest thing you'd do to me" . and of course my bestfriend told me and he said to my bestfriend that him and the girl were play truth or dare but i think hes lying. please help what should i do! :(