Does anyone have any experience with Microgestin BC??

I have been on Microgestin fe 1/20 for not even 3 weeks, and I'm gaining weight, not able to lose ANY weight, no matter how healthy I eat or how much I exercise (I usually drop weight fairly easily). I got the Mirena IUD removed right before I started the pill, so I'm not sure if it's just my body still adjusting...ALSO - does anyone know how long until the pill is effective with no backup protection? I have actually missed a couple of days (oops) so I know it's not effective yet, but wasn't sure how long (once remember to take it on a daily basis) until no backup protection is needed. TIA!