I'm 15 and my boyfriend is 22 ?!?!?!?

I'm 15 but I don't look 15. I am tall and have blonde hair to my butt I am on the swim team and I'm very smart I'm also graduating a year early.

A few weeks ago my parents were out of town and I actually just got back in town a few days ago for my dads job, And it was over fall break at my brothers decided to have a party invite some of their friends from high school. There are you graduated. I met this guy named Josh who was 22 but I didn't know he was 22 at the time And I also didn't mention that I was 15. We ended up hanging out all week and all of last week my parents still weren't in town. We did not have sex we made out a lot, He brought me flowers to my swim conditioning, Took me out to dinner, Take me fishing etc...

The last night I went out with him Secretly, And he proceeded to tell me that he was 22 years old. He's in college to be a doctor. And didn't know that I was 15 but he said he'd like to keep seeing me... I don't know what to do... Any advice? This is very serious