Re: private part problems
There are various species of yeasts (unicellular fungus) that naturally live on our skin and contribute to decomposing our dead skin. This yeast is also what makes ears, feet, hair and skin everywhere smell bad if we don't wash it (for a long time).
It's possible you're having an allergic reaction or other skin condition (like psoriasis) that's causing the itching, but it's very likely a skin infection. Jock itch is a general term that includes fungal and bacterial skin infections in the groin region. More often it's fungal, but bacterial jock itch happens too. (Interestingly, bacteria affected skin glows a coral red color when illuminated by a black light.) As jock itch progresses, sores may develop in a random pattern. You may even see tiny pimples or pustules with parts that are red and dry. Small scales may develop. The infection becomes more irritating as time goes by. In severe cases, the skin breaks down more and it becomes very uncomfortable.
When you say that you know it's not jock itch, is that because you have tried jock itch treatments and they were no help? There are different ones and some are so weak they don't really do anything. You want to be sure to get a stronger treatment. The stuff women take for vaginal yeast infections (mycelex/lotrimin/monistat) is often stronger.
Avoid moisturizing soaps that can leave a residue. The residue disturbs health skin ecology. For the same reason, avoid using oil/fat-based lotions to masturbate. You might find you need to use a wash cloth, loofah or sponge to exfoliate your skin better to really clean it.
I like Neutrogena T/Gel shampoo (liquid soap). It's anti-fungal. I wash my ears with it and they don't smell funky after 36-48 hours like they would otherwise. The pine tar in it radically reduces sweating too, so it could help your itch a lot.
Jock itch (and skin fungal infection generally) is associated with damp skin, sweating, friction/abrasion and tight clothing. You might find it helps to let yourself dry off thoroughly after showering before putting on your clean underwear. You might find it helps to wash your laundry differently--with either a stronger or less residue-forming soap. Borax is a mild anti-fungal laundry detergent additive that might help to use.