I've heard of Erythema Nodosum but wasn't sure what it was, god you poor thing, that sounds as nasty as all the other lumps and bumps that we've been talking about.
I must admit I think I'm pretty symptom free at the moment - apart from the usual bloating, cramping, the big "D" and then the other, constipated - but that all only happens maybe once a fortnight....but the abscess problem makes me think that I'm having a flare up too....it's all inflammation after all. So you may be right in that you're having a flare up with your fistulas giving you trouble. I can usually tell because the hospital will ring me and ask what problems I've been having as my white cell count was a bit higher than usual and viscosity levels too - all to do with inflammation - so when I tell them yes, I've got yet ANOTHER abscess they say "oh, that would explain that then"!!!
If you have got a fistula and you're worried about it - I would definitely go and see your doctor, because if these get further infected they can be quite dangerous - I don't want to worry you, but you should really get it checked out.