I can't keep up the 2nd round

So my bf cums pretty quickly the first round we have sex, but then the second round comes around less than a minute after and I struggle to keep up. Oh my god, I don't know if it's because of how good he hits or because I cummed already but damn I need to find a way to last longer. We check my covers and halfway through the second round we realize I left a huge wet spot on my bed. And we're not able to finish the second round with him cumming because my vagina starts to throb