What can I do now?

When you gave him the brush off during Jan-March you kinda cooled him down. When he was making it clear that he wanted to hang out with you this summer did you make it clear to him that you wanted to hang out too? Or were you kinda neutral or like.. hmmm ok kinda thing? Now that he's busy with sports he may also be busy talking to another girl like you were talking with another guy during the first 3 months this year. Just keep the contact with him however you've been doing it in the past but don't run after him because if you do, he'll take that as being desperate, and that usually cools a guy down on a girl when they start being too available. Just talk nice when you get the chance and flirt a little. It's ok for him to know you're available and that you find him pretty cool or hot however you feel. But that's enough. Leave the rest up to him. If there's a chance for things to work out in your favor, it will just by you keeping in good touch with him without running after him. It's better to be a little scarce than too available. Good luck!