Question for already moms

Im 29 pregnant with my first which was never supposed to happen due to severe pcos buth the pregnancy has been really tough im 27 weeks high risk and this will be the only one for me five years ago i was 447 pounds pre pregnancy i dropped down to 278 pounds now currently 286 so as u can tell im a big momma well my question is after ur first baby what was the best birth control that you went on that did not make u gain weight i refuse to gain a bunch again