Gall stones can suddenly become lodged in your bile duct, so if you get down with crippling pain, go to the ER because that's a likely source of the problem and the GB needs to come out immdieately to prevent a serious infection.
But, without crippling pain, you're probably right the gall stones aren't the cause of the problem, especially since you notice bowel problems with stress. Whether this is IBS or not is iffy because it's actually quite normal for people to get upset stomachs and bowels with stress. According to the Rome II Criteria, your problems have to be on-going (although not necessarily everyday) for three months before you are labeled as having IBS. That weeds out short periods of stress and intestinal bugs that can sometimes linger.
Are you where you can walk outside your home, or take transportation to a nearby park or school track? Or can you afford a treadmill (find them on Craiglist cheap)? Walking is a GREAT stress reliever; if you could walk as soon as you feel stressed, you might could prevent your attacks. Walking also helps regulate bowel movements to some degree, can reduce acid reflux and it can start to help with the weight problem. Also, when the kids won't go to bed, make them walk with you. They'll either tire out quickly and WANT to go to bed, or they will get fit (a problem among kids today). Even if you can't walk, you might try yoga tapes or other low-impact workout tapes. You should be able to find some for free at the local library, although there are usually a lot of workout tapes at thrift stores too.