It could all be in your head. That's probably the most common source of problems like this. It could all be your emotions running away with you, so to speak.
Or you might have an infection. Yeast and bacterial infections are common and sometimes can go unnoticed while causing symptoms like these. Getting checked by a medical professional is the only way to know you don't have a simple infection (and/or inflammation/irritation/obstruction) that's causing your problem that could be cleared up very easily.
Cranberry may help prevent urogenital infections in the future. You may find other dietary choices you need to follow to be less susceptible to future infection.
Or you may find you need better hygiene to minimize your chances of future infections. Intact/uncircumcised men (with average length foreskin) should wash within a few hours of sex or masturbation in order to keep semen residue from decomposing anaerobically in the urethra and foreskin. Semen can be flushed from the urethra by urinating, and the foreskin can just be kept back to keep the residue from decomposing anaerobically. But if you keep the foreskin forward (closed) most of the time, it needs a light fingertip rub with water to clean off any residue. (The entire penis wash (including pubic hair) only takes about a minute.) I use soap, but people with more sensitive inner skin and glans mucosa might just use water. Definitely avoid "moisturizing" soap like Dove. The thick oily ("moisturizing") residue it leaves can interfere with the healthy skin microbe ecology especially if you have sensitive skin. (Maybe you already knew all this. No offense.)
You might improve hygiene and rapid ejaculation time to retract your foreskin leaving your glans exposed for hours at a time during the day. This makes the skin toughen (keratinize). The tougher skin is more resistant to infection and less sensitive, so you'll last longer. Note: you can only do this safely if your foreskin retracts fully and easily with an erection. If it doesn't it may need stretching (just to be able to enjoy sex fully). Here are directions:
http://www.healthboards.com/boards/mens-health/178155-stretching-fix-tight-foreskin-phimosis.html
Or are you on any medications that might cause your symptoms as a side effect?
Or another less likely thing: your hormone levels could be off. You might find getting more sunlight helps your sex drive. Also I like chocolate for that--but never cheap chocolate. It's just sugar and garbage. The only chocolate that could be thought to be somewhat healthy is the premium dark stuff with low sugar and no (powdered) milk (IMHO).
Of course there are tons of other things it could be too. Check with a doctor if you haven't yet.
