My girlfriend makes me feel like I'm the problem

A few days ago, I told my girlfriend that something she did made me feel insecure, and her response was saying things like, “I already lived that, I was 20 once,” and other invasive comments. She minimized my feelings and basically made me feel like what I was expressing didn’t matter.

It felt like she saw me as the problem just for telling her how I felt. I don’t know if I’m explaining myself well, but it was a really uncomfortable moment. For context: I’m 21, I just turned 21, and my girlfriend is 31.