I wouldn't say directly related - however certain medications can cause issues with that. Best thing is to get checked by a doctor.
I think it is related to just being diseased in general, rather than crohn's specific (i.e your body starts to shut down some functions if it is fighting disease elsewhere in the body). I know I have had similar problems during a flare. Prednisolone may also be a contributing factor as well I think as I've noticed similar things while on that. I also noticed I had problems getting "it" up on occasions and a lack of sex drive during the same period. All related I guess. Although these issues didn't last more than a couple of weeks for me, so you should probably get checked out especially if it's still a problem once your crohn's symptoms subside or you are off the prednisolone.
Well, one bizarre possibility is that a fistula intersected vas, or seminal tract someplace. It's a long shot (no pun intended). Overall health, diet, meds, depression, could be the culprit as well (individually or jointly).
Cozmo,
Are you able to get it up? Are you able to achieve orgasm despite the fact nothing is coming out. Certain drugs can do that, one in particular is called Silodyx (Silodosin), it's used to treat BPH and being studied for use as male birth control.
Welcome Cosmo,
And sorry you are going through this. What are all of the medications you are taking? If you have the time, try to research side effects of your meds, both short term and long term effects. Medications can definitely have an impact on your lower region when it comes to things like arousal and other reproductive system functions. I have noticed this to be a common situation for many women on here with IBD so I wouldn't rule out one or more of the meds contributing to your situation as well.
Keep trying to create dialogue with your doctors and if they can't or won't give you answers, there's nothing wrong with finding a second or third opinion if needed.