I responded terribly to the depo-provera shot. mood swings, breakthrough bleeding all 3 months, weight gain of 30lbs. would implanon affect me the same way?

It could: The Progesterone in Implanon is different than the Progesterone in Depo Provera (medroxyprogesterone) plus it is a lot lower dose. That means you are somewhat less likely to have the side effects you had with Depo-Provera provera. Remember that Implanon can give irregular periods, but is much less likely to bleed for 3 months, or to cause much weight gain, and less likely to give mood swings.