Is he serious about me?

Help, I need advice. I've been dating this guy but am not sure if he's really serious about me. We always have a good time when we hang out but then he'll be MIA for days or even longer than a week and won't even answer my texts. Sometimes he texts me to ask what I'm doing but won't respond after I answer!! So frustrating! But then when he comes back, he's really nice and acts like my boyfriend and has asked me to hang out with his friends. What do you think? I know he has a lot going on right now and maybe he's scared?