Does anyone else have this problem?

i am 18 and i have had before but i seem to get nervous before ? do any other guys have trouble "getting it up" because it was my first time the only other time i have done it and it took a lot to get it up and when i finally got in i wasn't that horny and i couldn't finish. does it just mean i didn't like the girl enough because i have heard before that "p*ssy is p*ssy" blah blah but idk when i had it wasn't that great. any advice on this subject would help me greatly