Also, weight fluctuations (both gain and loss) are noted side effects of hormonal birth control. However, most of this is due to water retention and sometimes increased appetite. You've had WLS, the likelihood of you gaining significant weight from something like this is slim.
If you start on the pill, you have the option to try several different types until you land on the version that works best with your body
Find/talk to your gynecologist, you'll be able to ask more in depth questions that are particular to you <3