Sure, it would be different than anything that you'd experienced before, but...
Fuck if Jack didn't have a good point. He was always hot as hell to you, and standing up, eyeing yourself up and down as you lifted your new belly. Leaning back, your posture needing to change completely just so you don't collapse to the ground, you heave your nasty belly onto the decrepit sink. Some hairs catch on the various grime on the sink, and you feel your balls churn as your erection tries to return.
The new size of your tiny cock was yet another gift that you wondered how Jack knew you so desperately wanted. With what you know now, your mind slots into place, the choice was made for you long before you ever became friends with Jack. You would have ended up here, a nubile slob on the precipice of a raunchy, rancid eternity, either way.
Your decision was made. Not knowing how you were supposed to apply the ointment to your mind, but finally letting yourself fall deep into the depravity you'd held off for years, you desperately begin spreading the ointment on your eyes and your newly bare scalp. You keep rubbing it in, while performing some facsimile of humping desperately trying to satisfy your arousal. Before you even know it, you begin to grow hornier knowing that having finally fixed yourself, gotten what you've always wanted, there's no way you'd be able to satisfy yourself this way, especially with how small your cock is. So much time in the bathroom ensured that as you belched out gas for longer than any normal human could, echoing through the halls of the wretched home, Jack's mouth curling into a smile as he heard the echoes, your precum barely dripped out, needing far more action for release.
As your mind locked itself into its most depraved nature, new desires awoke in you. Shedding the shackles which kept you clean, you finally felt free to express your most basal desires to yourself.