So me and my girlfriend have been together 2 and a half yrs and we have NEVER had sex , we have tried plenty of times but everytime its time for me to insert my penis into her virgina my penis gets SOFT through out foreplay i have a full erection its just when it comes down to the sex part when my penis goes on soft ive been trying hard to relax but nuthin will work i talked to a dr and he advised me to relax more...how do i get over this sex axiety someone please help me im goin crazy....how can i keep my erection witout medication im 19!