Horny Goat Weed and or Maca, Zinc and Folic acid (together) but be careful with zinc supplements, too much is bad for you.
There are supplements on the market that help increase 'sex drive' (NOT) but they [bgcolor=#E10000]might[/bgcolor] help increase fluids.
Don't buy the most expensive as it has a little of these as the cheaper ones. It is best to try to get the real plant material, but read up on them.
In general, stay away from mail-order pills sold by less-than-reputable companies; you really don't know what's in them, and their claims are almost always untrue or at least greatly exaggerated.
Here's a page that can tell you more about things like this:
http://www.jackinworld.com/questions-answered/jackinqa-and-qa-archive/semen-ejaculation.