I had problems with the injection. I was on the three month one and every three months I picked up 3 kgs. i have also recently changed contraceptive from the pill to the mirena, and I was told by the gynea that it could take up to 6 months for my body to adapt to the change. currently I experience a lot of water retention and my weight isn't moving. so it could be that your body doesn't respond well to that type of contraceptive or that you need to bite the bullet and give your body some time to adapt.