me and my girlfriend went about 5 rounds we broke them up into random times and its our first but every time we go at it i dont feel like im going to cum anytime soon and i feel like i can keep going but there is a stinging sensation that lasts for a few seconds is that normal and means i cam or do i just have a high endurance she cant last to long cause she gets tired or her knees give out but if the stinging is me cumming i dont react at all i just keep going and going like nothing even happen hope there is a good reason and she does feel good im just worried and feeling like i am letting her down each time i dont bust i also feel down i trie to hide it but im sure she knows so if any one can help please?