Rectal pain before bowel movement

I am a 52 year old female that for a year or so now suffer with very occasional but intense pain in my rectum.  It took me a while to realize that it only occurs a short time before I am ready to have a bowel movement.  It has a few times woken me up in the middle of the night, as most times I have a bowel movement in the morning.  It starts out as an ache and then grows in intensity and then it's gone just as fast, lasting less then 5 minutes.  I suffered with IBS years ago when I was younger but don't anymore.   I am on a lot of medications now for other problems and do have problems with constipation from time to time, although not too often these days due to one medication I am on that causes the opposite problem.  This pain problem only happens once in a while, sometimes with months in between occurrences.  It is only in one specific spot on the left side of my rectum.  I have noticed absolutely no visual blood at all, whether I was constipated or not.   I spoke to my physician who scheduled me for a colonoscopy, my first one, but that is not until next month.  Needless to say, it has happened enough times now and I am, quite frankly, scared to death and at this point, losing sleep.  Does this sound like something serious?  I know that it's not possible to diagnose in a forum but are there other possibilities that this could be?  Or does this sound like cancer symptoms?   I have had four children (large ones) and I know that I do have resulting hemorrhoids that are outside and don't bother me anymore.  I read that there are internal hemorrhoids as well because my sister had similar symptoms, had tests done and got that diagnosis.  I do get bloating but have had bloating problems my entire life from an under-active gall bladder that started  long before any of this happened. Any information would be greatly appreciated....and thank you.  

[LivingInHope]

I would guess perhaps a fissure, but you don't see any blood.  I get pain with hard stools and bleeding and all they found was an internal hemorrhoid, which they say typically causes no pain!  I had a fissure in the past but if it's there, it must be so small the GI people who have looked can't spot it!  They insisted on a colonoscopy after I did occult blood stool testing that came back positive times three.

   Also, an immediate relative of mine had a polyp close to the opening (don't know if it caused pain though).  The polyp was removed and found to be non-cancerous in her case.  Can you get some occult blood stool testing while you are waiting for your colonoscopy?  Also, are you on the cancellation list in case a sooner date comes available?

[mammo]

Polyps won't cause pain, but rather bleeding.  But they can become large enough to make passing stool difficult.  I think if it were anything serious you would have bleeding and more pain.  Gas can cause severe pain as well.  I truly feel that whatever it is you'll be catching it early and that's what important.  I wouldn't worry, and it doesn't sound like cancer.  I've had a lot of this in my family, and none had these symtpoms.  Take care....