Erection difficulties and irritated penis

Hello,

I've been having issues, off and on for a little over a year, in getting an erection. The issues seem to happen every other month or two. I can gain a very erect penis and everything is normal, then a month later I have to strugle to get and maintain one. Also, I've noticed when masterbaiting, that after I have ejaculated I have an actual orgasm seconds later, which is sometimes a little painfull. After this, my glans is very sensitive, red and irritated, and hurts when rubbing against my boxers.. then this and the erection difficulties persist for a couple of weeks.. then back to normal. I do not touch my glans at all when masterbaiting. I'm 24, haven't had sex for many years, and have been on corticosteriods for 3 years for another issue unrelated (hopefully!) and have been tested for STD's prior to having these issues (no intercourse since the test). It's really starting to affect my personal life, Any ideas??

I thought it could be the meds or a hormonal imbalance...Just don't know!

Sincerely,
Confused and distraught