Women (and other dickgirls under the right circumstances.)

You've always had a problem with constant erections when around an attractive female form, and you think you'd be OK if they have a dick in the right situation.

Only with a significant application of will can you prevent an erection when near such, even if they're family members. Your overactive imagination will kick into gear at the slightest provocation, filling your cock with blood and making things quite uncomfortable.

You've never had sex though, as you were raised in a conservative religious household, and your parents trained you to hide your "extra" endowment. Nearly every day you were sent to your room for an hour or two because you got obviously aroused simply by some glimpse of your mother or sister's body, even covered by concealing clothing as they usually were.

But all this really did was train you to hide it at all costs and masturbate multiple times a day in private.

Constant masturbation has trained your output to a significant level, your ejaculations are massive and your recovery time is short. You don't have much stamina though, as you've usually masturbated purely to make your erection go away, and the faster the better. These days it only helps for about 15 minutes though, for some reason your body seems hellbent on a constant erection.

Your parents homeschooled you through highschool level to keep the secret, and you've started taking courses online for an associates degree in a computer field that will let you work from home.
However, the degree has several in-person classes that are required, starting in the second year.

You're not sure how you'll manage it, but hope that most of them involve sitting at a computer desk which will hide any issues.