Cramping in lower abdomen late in day and evening only

These cramps appeared after taking two kinds of antibiotics for sinus infections.  At the end of the second run, I got these weird cramps in my lower abdomen.  They only occurred later in the day and in the evening.  After awhile, they started to occur in the daytime.  They seem to come and go.  Lately they've only been in the late afternoon and evenings into night.  I usually feel the cramping go around into the tailbone region.  It's a really strange thing and no doctor has been able to figure it out.  No, H pylori, no Cdif.  But yes for yeast in the stool.  Not sure if it's the cause, but I've started the strict candida diet and I will be taking antifungals soon also.  We'll see if it works, but I'd really like to know if anyone else has these kinds of cramps.  I've had ultrasounds and colonoscopy and endoscopy.  I'm postmenopausal (2 years), but these cramps feel almost premenstrual.  
Thanks!

[ggreg]

Sometimes antibiotics will cause some terrible indigestion in some people.  Those drugs tend to dry out a person's guts and also they kill both "good" and bad bacteria.  The good bacteria helps break down waste.  So, could be you are constipated and this can cramp up a person.  There are several solutions to this, and one of them is to reintroduce the "good" bacteria by drinking Acidophilus milk or eating Activia yogurt for a couple weeks, they have probiotics in them that put the good bacteria back into the intestines.  Also, drink extra water for a while, exercise regular (activity helps bowels move), and eat enough fiber foods, like whole grains and fresh vegies (like oat cereal and frozen broccoli and raw carrots).