Ok, I think it was the fact that I had masturbated earlier that day and had a lot of wine right before.

On the second time, I was able to get erection instantly. But this time, I shortened foreplay a lot and just put it in right away for fear that it would go away. But she was very dry so it actually hurt my penis (didn't use condom). I thrusted really hard trying to give it all I got, but my penis eventually went numb from the pain.

She seemed to be fine with it, and then wanted to get on top and ride me. But by then I had already been thrusting for a while, and when I turned over, the numbness made me lose erection. Also gravity doesn't help.

I then went down on her and after a little, I got hard again (I get really turned on going down on her), and she rode me for a while, but I think the pain and numbness was still in effect and I couldn't really feel much, and after a while I lost it again.

I think it was just the initial dryness and too much friction. Next time I will use a lubricated condom or put lube first. The sex didn't feel good. Our relationship is also not very intimate on other levels. I think we will break up.