Well I had the mirena placed on June 26 2011 and I have had a regular period but I feel like I'm pregnant since my breast and belly look like I am pregnant I am really worried since I have been drinking and having second hand smoke. Is there any chance of IF pregnant child have birth defects?

Possible, depending on how much you have been drinking. Of course it would be wise to determine whether you are pregnant or not. It would be unusual, but not impossible for a pregnancy to occur with an IUD in place.