He gets soft everytime

Hi, I have a new partner been together 5 months and I notice he gets soft fast or he can’t fully get hard??? Or if we have sex he can’t go again till hours later. First time going through this and I tried talking to him just because I’m really curious and want to know what it is and he swears up and down like I’m crazy and there’s nothing wrong???

It’s frustrating because I’ve messed around a lot in my younger years and never came across this until now, it’s a every time thing. He doesn’t fully get hard or if he does he automatically hets soft, anything I can do to help???