If he only asks me out once a week or so, is he not really into me?

If it's been a few months and you're not satisfied with what you're getting, it's time to speak up about it. That means essentially having the very conversation that many girls are warned scare men off. There's nothing wrong with having expectations/wants/needs, but it all comes down to expressing that in a non-confrontational or demanding way. In your case, it's definitely a good sign that he wants to see you a couple of times a week and that he does call you. My question is this though: are you initiating most of the "dates/hanging out" and the phone calls? If so, step back and let him continue to put his effort in. If he initiates more, great sign. If nothing changes, it could be time to cut this one loose. He definitely seems to like you quite a bit however, if after a few months, he still content to stick to that same routine, it may be that he isn't as interested as you thought (at least not as interested in whatever relationship etc you may be looking for).

Go talk to him about this. Choose your wording carefully though. Don't just go up and say "we need to talk". This tends to put men on defensive automatically. Just casually bring up how you enjoy spending time with him (you know, talk about fun memories etc). If he agrees and talks about some good memories (without a bunch of prompting on your part), it's a good sign. Tell him you're curious as to what he's looking for relationship-wise. If he's not that into you, here's the part where he might freak out and bail. If he's into you but just needed to see some mutual interest from you, this could be where he decides to step things up. A lot of men tend to get comfortable too quickly and you may have to change things up a bit to get his attention.

As to whether more time dating could step up his interest level...there's ALWAYS a chance for that. Doesn't always work though and you usually shouldn't waste time trying. This means that the moment you start questioning whether or not you're wasting time, it means you're beginning to want more. Find out if this guy is looking for what you're looking for. And if not, be prepared to move on to someone else. A few months is NOT a long time, particularly to a guy (as guys tend to take more time than women getting to the point where they'd like a relationship); however, this doesn't mean you don't go after what you want and leave what doesn't work for you.