I have been on Levoxyl for only 12 days after switching from gene...

I have been on Levoxyl for only 12 days after switching from generic Levothyroxine, which I was on for 3 years.. I have no history of any GI disturbances and the last 5 days I have been extremely constipated, had horrible stomach cramps, gas and bloating. I am on no other meds, so my Doc and I have concluded maybe Lexovyl is not the right med for me?. Am starting name brand Synthroid tomorrow. In addition to the GI disturbances I have been having headaches the past week as well.