1.If you are in doubt if he cares about you or not, then he probably does not, unless you're a very timid girl who has difficulty believing that HE could like YOU.
Or maybe it's YOU who doesn't (yet) like HIM and you don't want to try to develop feelings for him unless you know he's honest?
2.Is there any reason he might be lying, like just getting you in bed, getting a promotion in your dad's firm etc.? If you've already slept with him, chances are he means it. If you haven't and you're not saving your virginity till you're sure you may just do it and enjoy it, though try to fall only a little for him. Even if he was lying before, the lie may still become truth...
3.You don't seem to trust him - either because you don't know him well, (then get to know him: talk with him, hang out with him(take care),spend as much time as you can with him)
or because you know he is untrustworthy. Of course even a habitual liar may tell the truth: if you are and stay a very independant person, maybe you can be happy even with an untrustworthy guy.
Answer
Action speaks louder than words. Does he show you that he cares about you? Does he make you feel like he cares about you? Forget about what he says.
4.I think that you know that a guy really cares about you when he shows patience in if you have a time during the month that sucks! I think that actions speak louder than words with guys, and they can show it better than say it.
5.Definitely behavior. How well does he consider your feelings. Does he include you in his activities? Do you feel like you are part of his life or a bit on the sidelines? Does he talk openly with you, or does he keep secrets.
I don't necessarily agree with all that is above. You must ask yourself first...does this man show me that he cares for me? Would he drop everything for me in my time of need? Not only that, but does he think of me as being the most important thing and everything else comes in second and so on??? If you want to get to the bottom of it then test him, don't lie though. For example: I was in the same situation...I was curious to figure out if this guy I dated for 2 years on and off if he seriously cared for me...he said it, but did he mean it? What I did was I went and visited him during a time of our seperation. He had a weeks notice that I was coming. So, I got a hotel room and I called him to let him know that I was in town....he didnt show up until 12 that night. I was so furious, but before you jump to conclusion such as I did ask him what he was doing and so forth. Needless to say, I now dislike him very much...he was the kind of guy that will tell you anything to see you happy in the present time, at least when he was around. I learned my lesson so now when a guy says he cares I act as if I believe him, but secretly I test him. I am a successful career oriented woman so regardless of age, the testing will always determine the final solution.