My friends think he's probably cheated.

I've been with my boyfriend for a year next month. I am 21 soon to be 22. He's soon to be 23. Before we got into a relationship he was having mostly casual sex including one night stands...probably until several months before we met or so.  I've never had sex so I told him I wanted to wait, not til marriage but in general. Its a lot serious for me and I told him I couldn't til I loved someone. I love him, but I'm still waiting. He hasn't pressured me at all but before we became official he said he wanted to have sex within the first week of us meeting. My friends are all skeptical. They like that he's waiting but they don't think he's capable of waiting given his love for casual sex before meeting me and they think he's probably getting it somewhere else. He said he doesn't mind waiting for me but even my guy friends are telling me that someone like him probably wouldn't wait a year and now I am just over thinking and don't know what to think. (Ps. We are sexual and do things, just not intercourse yet.)