Guys, thanks for all the replies, really helpful. I'm not exactly new to BB, I've always barebacked with my 4+ years BF, but initially I was on the bottom side. In the last couple of years I've been more on the top side and we've been piggies (3 somes, sex parties, cum dumps) and I started being more bothered by this problem.
Jerking off: I noticed it too. If I don't cum in a couple of days, I don't last at all. I'll try to jerk more often when I'm piggie :-)
Multiple cums: I wish, but never happened. As I said, I noticed that several times I stay hard after cumming, but my interest in fucking the sloppy ass goes down (maybe because I get frustrated that I already unloaded). I will try to keep fucking next time!
Sex pills, like the ones you can find at theses stores here in SF (e.g. Lightning rod): I tried them a couple of times, different brands. They seem to work, but I'm not sure if it's just a placebo. Any thoughts on them?
Finally, I think I just need to have more sex and fuck more willing bottoms here in SF