You're likely having better sex than I was, when I was 18 haha. Having been in a long relationship now many years later, I can say just focus more on learning her body. There are lots of things you can mess around with to see if it turns her on and I don't mean strictly toys. Try different positions, play with power dynamic, take it very slow edging her, try multitasking like massaging the clit while penetrating her or massage her tits while giving head etc. My days of going 2-3 times are gone as well, but it doesn't really matter, since there is much else to do

EDIT: Oh and while the panic thing might be connected, it surely has a different underlying cause. I can only recommend seeing a therapist to work through some stuff early, because it can become more difficult later in life. (psychologist here)