Me and my gf never had sex and decided to have it couple days back, it was going well and we thought we are ready for it, i had my erection on when i wore the condom. but after few minutes it felt like something is wrong and i started losing my erection. i should mention that i was a bit tired from the journey and i needed some sleep. but apart from that i was really excited and seduced too. i lost my erection and got it back soon but it wasn't the same before i put the condom on. Is it normal?