I am 18, not a virgin and I still have problems getting a penis in me. Sometimes its slightly uncomfy... I think the idea of something going in me makes me really nervous and I tense up even if I want it. And that makes it very weird
Adive or tricks?

Stay relaxed and use a good amount of lube. Not jelly, it will get sticky and dry. I like the KY sensitive liquid :) Good luck!

I would get a dildo and/or a vibrator. Get used to that feeling. It will help you relax.

If you're uncomfortable than use lube and go slow. Just concentrate on the feeling.