Can't stay wet

Alyssa • it's moderately lit. | 20
My boyfriend and I have had sex twice but I couldn't stay wet (because I was nervous). I know about lube and we plan on using that next time, but can anybody give me tips on how to relax??? I tense up therefore my muscles in my vagina tighten up, that and me not being able to stay wet makes it really painful for him to enter me.