Green stool and acid reflux

Hi! i'm 21 years old. I usualy have very normal and healthy B.M's, but recently I noticed a bright green color and film (or muscous) associated with my stool. The night before I was having some stomache discomfort and I took some heart burn medicine. I do have acid reflux and have had stomache ulcers before, but I've never noticed this in my stool. I'm concerned because the stomache discomfort has not gone away, I have not been having normal B.M's (I usually go 3 times a day and haven't been able to go, but once) and I have not eaten or drank anything with a distinct green color (besides a salad I had the day before). I've acctually been eating less greens than usual. I do take zoloft for anxiety and have been under a bit of stress lately.

I know that green stool can be contributed to excess iron in the diet, dietary supliments and rapid bowel transit time.
I have no idea what rapid bowel transit time is or what causes this. Can someone PLEASE shed some light on this issue so that I may know that there is no cause for alarm.

Thanks and sorry for the odd and grotesque subject matter