Problems with low stamina :-(

I have noticed lately that after orgasm I get very tired and over-stimulated and just want to be left completely alone. Up until the past couple to three years I was able to cum several times in a row, non stop. I still have a good sex drive, and can obviously cum, but it's a one shot thing. This is depressing to me since I feel at 25 I should still be at my sexual prime. Does anyone else have this problem?