You mean pep not semen, I assume. Plenty of ways to get semen back in your life.
I guess the first recommendation would be to sleep more. Though if you needed to go to the internet to know that more sleep equals less tired, you probably have a larger problem with the way your brain works. I can't help you with that because you most likely see only shapes and colors.
Fatigue is a fat, fuckin' bitch, and almost isn't funny at all, unlike a real life fat, fuckin' bitch like Roseanne. Not sleeping enough affects everything. You're cognitive skills as well as your genital function, two of the most important things to being a happy person. In fact, I'd say understanding the world around you though an alert template, knocking the fuggin' booty, and getting lots of sleep are the three most important things in life. Maybe a fourth would be drinking plenty of fluids. Fifth would be laughing. Sixth would be hitting that ass again, or hitting your own ass, I guess. Just making sure your ass has been hit on a regular basis.
If none of these things work, go to the doctor and fuck him.
Short Answer: Seriously, don't struggle through life being tired. See a medical professional and get drugs. I suggest the ones that make you not give a fuuucuucckkkckk...