Aaah! Bloody doctors. While psyllium can be helpful, it is also know to CAUSE gas and bloating (which translates to pain in some IBSers! - including me on a bad day). Acacia is a hell of a lot gentler I promise. I don't even notice taking it- except that I'm usually pretty stable!
As you've gone downhill quite quickly, you should really have tests again. You might have an infection or something that's making everything worse. So go and get bloodwork and a stool sample tested. Hopefully an answer will come from that.
Have you tried enteric peppermint capsules? If you can tolerate peppermint (I can't) then they are a GREAT anti-spasmodic. Heather says they work better for her than prescription meds. You can order them from Heather (a good idea if you get Acacia) or you can get them from health food stores or on prescription.
For my IBS-A, I found a low, daily dose of Immodium was extremely helpful when I was stabilising. It meant that I could get on with life and also that I could eat more fruit and veg without getting bad D. Ask your doc - you can actually get it in liquid form if you need a really low dose. As you're swinging (from D to C) so much, this might be a good idea for you - start off at a REALLY low dose and increase it slowly until it helps (without making you too C).
Also, with veg - this might be obvious to you - are you only eating well cooked soluble fibre veg? That's cooked carrots, apple sauce... It's the safest and gentlest way to get veggies.
Btw, please do list the meds you've tried as everyone else will wake up soon and it'll save everyone suggesting their favourite drugs if you already know they don't work!