Gym crush gone wrong?

So i 26F started gym 2-3 months ago and had a crush on one of the guy 31M there…it was just an eyecontactship kinda thing but then it gradually increases to hi hello and he started correcting my form here and there once in a while. But the problem is he sent me a req on insta and i told him i cant entertain him since i have goals in life yet to achieve. I asked him to be friends but now he is sulking and behaving coldly in gym. He keeps making faces when i talk with any other person in gym with a smile. I think my rejection is the reason for this change in behaviour. Can anybody help ke why he is doing this???