I had this problem with my current girlfriend when we first started dating. It’s just nerves man. When you really love someone you just want to make them feel amazing, so you’re scared that you won’t. Nerves get worse and worse and it gets harder to get hard (pun intended). Just gotta get past the nerves! Talk to your next partner and let them know how nervous you are and work through it. Start with some foreplay that always helps. Men need to get warmed up in bed as well. You’ll get over it and soon you’ll forget it was even a problem. If you want to get back with your girlfriend, then you gotta y’all with her. It was her first time so she didn’t know how to help you. Just know you aren’t broken and it will pass. A lot of men go through this! We aren’t machines. We get nervous and scared. So practice till it works and try not to think so much man, it’s just sex.