Please someone help me on this one?

I was unofficially dating this girl and I really liked her at one point. We were going really strong and everything was working out really well between the two of us. I didn't know how much I actually liked her but people had told me she liked me a lot, which made me like her more. We had a thing for about three weeks and by the end I was questioning myself if i still liked her, there was a period of a couple days we didn't talk (may not seem like a big deal but we talked strictly everyday). We started to talk after the period of time and it wasn't the same. We decided to split (she needed time for her sport and whatever else she has going on in her life) Although we weren't actually dating, I miss her a lot. More than I actually thought that I would have and it's my own fault for not telling her that earlier when the whole thing started. Is there anyway through the circumstances I can get her back? I don't see many options and I have no idea how to explain this all to her. Im not even sure she would want to listen but I really cared about her and I didn't even know it. Please someone help me figure out what to do I'm miserable without her. I know it sounds ridiculous that someone could like someone as much as it sounds for only three weeks but I would do anything to get her back now. I just don't know how.