I've been taking Yasmin for years, it really seems to help the cramps. Normally I barely get any cramps, maybe for a day and i don't need to take anything for them. I actually had worse cramps on the higher doses of Prednisone though. I wouldn't really have my period but the cramps were horrible! So bad I had to take a painkiller to tolerate it. I think the birth control pills help keep the hormones from dropping quite as drastically. I've been on them for probably 20 years but before that had horrible periods that woulds sometime come every 2 weeks.
I know some people on here have mentioned birth control pills make their UC worse, but I haven't found that to be the case. I had a very long remission (see my sig) and was taking the pills during that time as well. I take the packs back to back though so I don't have a period as often. Also seems to help keep the UC flares from coming back since I'm not messing with my hormones as often.
I had to have my period this week as my body was giving me cramps for no reason. Trying to taper Prednisone too - I decided that during this week I just won't taper - why make two hormonal changes at the same time. Hoping my flare doesn't come back. Hopefully for you it will just be like IBS symptoms and after the period they will go back to normal.