A change in hormones has been linked to flaring with some. That's why some of us experience symptoms around that time of the month or during pregnancy etc. I think it is probably unlikely but something you should prepare for just in case. As for the meds - maybe you want to change from Asacol to Colazal? I don't know where you UC is but it is great for left-sided UC and maybe it could be just the change you need to get you out of this flare. And of course - enemas. (I'm sounding like Quincy now). If you're not already using them - you should consider starting. The Rowasa is the same meds as Asacol and should be perfectly okay while breastfeeding.
Mamas Boys (aka KTM)
Colazal, Azathioprine, Remicade
Culturelle, MultiVitamin, Folic Acid, Viactiv