Oh man, I just wrote this huge thing for you and my computer crashed. Okay, let me sum up:
Your C. diff was treated and hopefully your diarrhea will begin to abate. That nasty bug can wreak havoc on your guts. If your diarrhea doesn't go away, you may have a tricky parasite. U.S. doctors and microbiology labs have no clue how to correctly test for parasites. You need to send three samples of your stools to someone who really knows their stuff, and they need to test for all the weird, crazy stuff that they don't normally see. They absolutely need to do a stool culture.
I lived in East Africa and parts of South America for months, and contracted several parasitic infections over the course of my travels. High fevers were the mainstay symptom (up to 104 degrees); diarrhea was always terrible, like 30x/day; stomach cramps could be absolutely debilitating. Three years later, I still have low-grade fever (around 100-101), very frequent and sometimes bloody diarrhea, and stomach cramps. IBSers tend to have a lot of colicky abdominal pain and alternating constipation and diarrhea. According to many sources, IBS should not cause nocturnal or bloody diarrhea (unless you have hemorrhoids), fever, or significant weight loss. If you have these symptoms, I would be very suspicious of an IBS diagnosis. There is probably something else going on that should have focused treatment!
Your diarrhea may improve on its own, if you're lucky. In the meantime, here are some things that have helped me intermittently:
1) Fiber supplements, like Citrucel - make it into a slurry, like a heaping tablespoon of the powder in 3-4 oz. of water. Start slow, once a day, and increase it as you can. Sometimes this causes gas and discomfort in people, which is why you need to start slow.
2) Imodium or Lomotil. These usually help most people, but you want to make SURE you don't have a parasite or bacterial infection before you take them.
3) Probiotics, like Lil mentioned, are a must. Acidophilus capsules - 4x/day. Yogurt is a good bet too.
4) Anti-cholinergics like hyoscyamine or dicyclomine can help with the cramps, if you have them.
5) A good multi-vitamin is important if you have a lot of diarrhea. Take it with food so it doesn't upset your stomach.
6) Stay hydrated with diluted Gatorade (Gatorade itself is full of sugar, which can cause worse diarrhea; if you dilute it by half with water, it's a better hydration tool) or Pedialyte.
I totally feel your pain. Did any of this help? Let us know how you're doing!