Lower left abdominal discomfort

I am 29, female, 60kg and 178cm tall.  I'm reasonably fit - exercise 2-4 times per week, including running/tennis/gym.

I have had persistant discomfort in my lower left abdomen for around six months.   It is mild - never painful - but I am particularly aware of it when sitting at my desk at work, sitting in the car, lying on my side, and during some exercise and sexual positions.  I also have tightness in my lower left back.  

Three months ago, I had an ultrasound, which was clear.  The radiologist suggested my problem may be digestive, and the Doctor, having felt my stomach, thought it might have been diverticulitus, given I had also been mildly constipated for some time and he thought he could feel some inflammation.  He prescribed a course of flagyl, which I took in conjuction with psyllium.  This cleared up the constipation. It seemed to alleviate the abdominal awareness, but if it did, unfortunately it returned again very quickly.   As eventually did the mild constipation.

I returned to the Doctor, and had extensive blood tests taken.  I declined to have a colonoscopy in the first instance, but instead had an abdominal CT scan first up.  Both my bloods, and the CT scan were normal (although the scan showed some faecal loading).  I am about to book in for a colonoscopy - which I guess will rule in or out diverticulisis - but it will take some time before I can get in for the procedure.

In the interim, after discovering there is some family history of gluten intolerance/lactose intolerance and IBS, I have more or less stopped eating gluten.  I've dropped a couple of kilograms and have one to two normal bowel movements a day.  Find it a bit harder to run without the same level of carbs!  And I'm definitely not a fan of Quinoa.  But on the whole, the changed diet makes me feel good.  Not sure if it is because I have a problem with gluten, or because I am probably eating more vegetables...

However, notwithstanding this regularity and healthy diet, the lower left abdominal awareness remains, as does the tight lower left back.   My main concern is whether it is something serious (which I would have thought would have shown up in the blood tests, CT scan), or something that may affect my fertility - I want to have children in the next few years.  I'm on the contraceptive pill and my periods are light but reasonably normal.  

Any thoughts on what might be going on or what I should do would be very welcome. : )  

[thj29]

sorry I know I posted this twice.  was trying to put it into the "expert forum".