Weight gain with Mirena IUD?

I have only had it once. I did gain about 6-7 lbs which is a lot for me, but its hard to say if it was Mirena-I had been breastfeeding my daughter who had extreme colic and literally could scream from 9p.m. to 5 a.m. some nights plus I was afraid to eat just about anything for fear it would make her gassy/colicky. So I barely ate or slept, until 2 weeks after Mirena was placed and the doctor put her on hypoallergenic formula. She finally stopped screaming 24/7 and I wasn't afraid to eat anymore, wasn't burning calories making milk, plus it was the holidays, so yeah, its hard to say. Now I am back to the weight I was before Mirena, I have had to work for it but yeah I can't necessarily say it is Mirena.