To get clearer information on how he’s feeling towards you, you need to ask more pointed questions. “Do you just want me for sex?” is not a pointed question. “Why do we only hang out twice a month?” is. The first question is open to an empty denial that leaves you just as ignorant as before, the second actually brings you closer to an understanding.
So let’s say you ask the question, and he says that he’s been busy. Ask him what he’s been doing that makes him so busy. A person generally has one main priority in his life. That priority doesn’t have to be you, but his relationship does need to be at least in the top five. And if you like him, your object is to make him put you higher up on the list.
His availability for a relationship is precisely the space left by all the other priorities in his life.
So if you ask him to do something, and he says he’s busy, you need to find out what he’s prioritizing over you. Work, school? Then you want to find out particulars about the priority. What’s the schedule like? Ask him to hang out on a different day. If he still says he’s busy, you’ve just found priority two. Work out the particulars of that priority.
Eventually you’ll find out where you stand on his totem pole. You can muscle your way up simply by asking, “Am I more important than X?”
Be careful, because this kind of thing can make a guy nervous and bolt. This is the “I’m not fucking around anymore” pathway to a relationship. Take it easy and don’t push too hard too quickly.