Agree with Scott. It could be many things, including the after effects of an intestinal/GI virus. I had norovirus a few years back and it threw my system out of whack for several weeks. Getting the lab workup was a good idea and may give you some indication of what is going on, but in the meantime Scott's suggestions are all good ones. You can try Pepto Bismol as well. You may also want to switch to a bland diet for a few days, such as the BRAT diet - bananas, rice, apple sauce and toast - to see if this helps thicken you up.