I feel self-conscious

Yesterday I was sitting outside in my parents' car with my mom and I was wearing pretty short shorts. They're usually halfway up my thigh, but when I sit, it gets higher but not really that high. And this man with daughters gets out of his car parked next to us and gives me a sneer for a while and then he walks into the store. I'm pretty sure he was staring at me because his eyes were directed at me. I think he disapproved of me wearing such short shorts. It made me feel self-conscious and now I try to wear my shorts longer and if it gets shorter, I pull them down a bit.
I like wearing jean shorts and it's summer time, but I feel self-conscious about it now.