Well when I got on phen my gyno (she is the one that put me on it) didn't say anything about it affecting the birth control. She normally tells me if something screws it up. I also was having my period every two weeks and it'd last almost a whole week..versus the 4 days at the most before. So far I haven't gotten my period again..so I'm hoping my system is all lined out now. It's been almost three months! It is about time!!!