Incomplete Bowel Movements, Sexual Side Effects

About 8 months ago, I noticed that every time I would go, it felt as though my bowel movements were incomplete. The stool would pass normally for a bit and then suddenly it would stop and I could feel a full/stuck-ness in the upper rectal area, and no matter how hard I strained (though I tried not to) nothing would come out; it felt as if there was some kind of "plug" that stopped any more stool from passing, though I still felt the urge.

I'm quite certain that I was (and am) not constipated because my stools would generally be firm to soft and bowel movements would be pretty regular (every day, every other day). I try to eat high-fiber and laxatives didn't help. Even when I had occasional watery stool/diarrhea, I would only go about half to 3/4 what I normally would and then I would feel the "stuckness" and nothing more would come. It also felt as though the rectal openning was becoming narrower (i even noticed it became more difficult to flatulate). There was no blood in stool and generally not too much pain but a lot of discomfort; it felt as though I was in the middle of an interrupted bowel movement for up to hours afterwards.

This conditioned seemed to gradually worsen, and it was manageable at first but there have been some other rather alarming side effects. Around the time I noticed this problem, I also noticed that I began to loose sexual sensitivity occasionally, especially when it felt that the bowels were severely backed up. I could still function (get erection etc...) it's just that the sensations were reduced, as if I was "numb" down there. This would last for a day to several days and I thought I was just imagining things at first, but this problem slowly got worse as well, and recently I have little to no sensation and it has been going on for at least a week. I'm 23 years old so obviously this is quite bad news. I know that blood flow is essential for sensation and i'm guessing that this blockage is restricting bloodflow to that area.I have also noticed increased difficulty urinating and some pain in the penile area occasionally.

Looking around online, I thought perhaps I have a prolapse of some sort, although I have not found any obvious external protrusions (although the rectum does seem to swell outwards to an extent if I strain).

When I went to see my doctor about it, he just kept insisting that I was constipated and told me to eat more fiber, drink more water, and come back in a month. I asked him to at least check if I have some kind of prolapse so he did a digital rectal exam and said he couldn't feel anything. Just yesterday I read about internal intussusceptions and I plan to make another appointment and insist that I have a more thorough examination to rule out any structural problems (and i'm almost certain it is).

Any advice/help is greatly appreciated!