hiiii anxiety in sex is common anxiety can interfere your act also for it you have to require proper knowledge and skills also open communication between both partner is must sex is mutual act and your anxiety is a part of thinking ab your performance so kindly talk ab it with your gf if she understand you and support you than your anxiety will go away easily just require to be calm and understanding feel free with your gf by time you will learn and become more confident positive thinking is useful nothing to worry about it happens with everyone when started their performance in any field so just relax thank you