if that is the case, then i would say its the senna. i have a similar reaction to senna, tho not as severe. if you google "senna + cramps" you will see that abdominal cramps is one of the possible side effects listed for that herb. the cascara sagrada may have caused it too, possibly.
the problem with taking an herbal mix is that if you have a bad reaction you dont know which herb or herbs were the problem. you have to take small portions of each one and test how it affects you, thats how i figured out that senna gives me abdominal cramps, so now i stay away from anything with senna in it. different people react differently to different herbs.
i would suggest you look into Oxypowder which a lot of people have had success with, its a Bowel Cleanse product thats made up of oxygenated magnesium.
have you had a bowel movement since you took the IF? having several movements is likely the only thing that will give you relief right now.
sorry about the long winded reply previously, perhaps there was something useful in it for someone.