I take several supplements that work for me. Try L-Arginine and Lysine in combination. The L-Arginine will give you a nice flaccid hang and sometimes more semen volume. Lysine helps some with semen, but it also helps keep L-Arginine from causing cold sores. Finally, I like to take lecithin. It is good for the brain and it helps semen volume also. All the above can be found at GNC.
I take Tongkat Ali in a 50:1 ratio capsule. The stuff increases your testosterone. It is very expensive and you have to take it for a while for it to be effective. Research this stuff before considering to buy it.