Well, I don't exactly envy you your job, Bperry, but at least you have one so you can afford the Welchol. I'm having to crunch numbers over here to see if I can afford, on unemployment, to see the dr to get mine refilled.
Welchol should stop your D within 30 minutes of taking it--the same as Imodium or Pepto. If it's not stopped, you need to take another one.
I currently take two a day. I think my MIL takes 2 or 3. There have been a couple of people on here with D so bad they were taking 6 a day. It doesn't get in your bloodstream, so as far as I'm aware, the only thing that will happen if you overdose on it is you will get constipated (that's when you know you're taking too much).
I take mine first thing in the morning, preferably at least 30 minutes before eating, because eating cranks my guts up. I would suggest that you also take yours in the morning if that's when your D is worst. Get up well in advance of needing to go to work, take your Welchol, wait 30 minutes, then eat and use the bathroom. Hopefully, after that, you will be good to go for the rest of the day.
The only thing about Welchol is that it interferes with the absorption of other meds, but this is really only a problem where you have really finiky meds that need to be absorbed as perfectly as possible, like thyroid medicine. You really should not take Welchol while on thyroid medicine, regardless of what time of day you take what. You may also need to be careful if you take oral diabetes medicine.
Welchol, when used over time, can cause deficency in fat-soluable vitamins, such as Vitamin A. This is, again, because it interferes with how your body absorbs things. I have been taking one multi-vitamin at night (as far opposite of my Welchol as possible so I can absorb the most of it) to counter that problem and it's been working out fine. I also take calcium supplements at night, because they can help reduce D too. The best kind is Caltrate 600 w/ vitamin D (generic brand of the same is fine too). For some people, the calcium is all they need to take to control their D. Unfortunately, I'm not one of them (it'd be mondo cheaper if it did). In fact, I don't know how well it helps my D at all, BUT I found, when my guts were tore up really bad, that got me back to normal (normal for me). I have since read that calcium helps soothe minor irritations in the GI tract, and I'm quite convinced that regular doses of excess bile acid in the intestines can certainly irritate them. I think that's what it did for me when I had myself really bad messed up: it soothed my intestines. So I take it as a preventative. That way, if I do get into something which upsets my guts royally, they won't stay upset for weeks.
Here are some of the things which I know to upset my guts: sugar alcohol (found in sugar-free products, this is a super bad no-no as it causes diarrhea and gas in normal people), raw apples and apple juice (both are natural laxatives), any raw fruit and fruit juice with a lot of acid (which is pretty much everything but bananas, which are a natural constipator), caffeine (includes de-caf coffee, which is not caffeine free), fast food, and anything deep fried in partially hydrogenated oil (although stuff fried in peanut oil is tolerable in normal, but infrequent doses). I'm also a bit weird about milk: I can tolerate milk products just fine (including ice cream), but just drinking milk or using it in cereal gives me gas. But if I get Lactaid milk, I'm okay. But, then, I can't eat an omlette, but I can eat scrambled eggs containing all the same ingredients in them as an omlette. I don't know what happens to an egg when my husband fries it crisp into an omlette, but my gut says it's different than a plain scrambeled egg. So don't ask me why I can eat ice cream but not 1% milk.
You might try getting your probiotics through yogurt. Unless you are really lactose intolerant, or have a milk allergy, yogurt is generally a good breakfast food for people with IBS (it's generally better tolerated first thing than proteins, such as meat or eggs). The calcium in it helps a bit with D, plus you get the probiotics in it.