any one else?

does anyone else's SO not get like super freaking hard during sex? I mean sometimes he's like fucking rock hard and I can see his veins sticking out but then other times he's still hard just not like veiny hard. I know it's just my poor self confidence but when that happens I just feel like he isn't interested in me at the moment. for instance three maybe four days ago we had bomb ass sex like I was so wet I had to drink a bottle and. ahalf of water just to rehydrate and my legs were so shaky I couldn't even stand up to walk to the bathroom. then last night it was good but not as great as before. we have been together for 3 years and relationship wise everything is great. at least I feel that way. idk if maybe he was feeling unloved or unwanted and maybe that's what changed it or it's because he is still sick but idk. it just made me feel like he wasn't attracted to me but I know he is because I can see it in the way he looks at me and how he touches me and talks to me. I'm over thinking I'm sure. how do you guys handle it? I know he talks about how he wants to get his testosterone levels checked and what not so could that be an issue?