Hello! Sounds like you could have IBS, but also diverticulitis is a possiblity. The pain in the lower left abdomen is the most common symptom of diverticulitis. All of the other symptoms you have mentioned could go either way for IBS or diverticulitis. I would get checked out because diverticulitis can cause serious problems if the infection gets too bad. Hope this helps a bit...
Sounds like it just may be IBS.
IBS and stress are related. The plus side is that you have no blood in stool :O)
Your worrying will add to stress as well.
Consider your diet, and try eliminating...oils, fats, greasy foods, sugars , high fructose corn syrup, coffee, spices, alcohol, dairy, and salts.
Cut back on these bigtime for a few days.
Make sure your are getting enough fiber each day..i now eat 12 grain whole bread each morning. Also a calcium magnesium supllement...as t will help with digestion.
Incorpporate more fruits and vegetables in your diet as well. Peaches, pears and banannas. Protien such as chicken ad some red meats that are cooked to be tender. Ground beef is a no no. Pork is ok as well.
You may also want to consider, ways to reduce your stress.
Meditation, guided imagery, bio feedback or your doctor can prescribe something if you wish to help with worry and anxiety.
Hope this helps..keep us posted.