Hi, I Was Due For My Depo Shot Yesterday But

Hi, I was due for my depo shot yesterday but decided to get off of it due to weight gain. I am switching to the Nuva Ring but they told me to wait until Sunday to put it in. I read that people don't start to lose weight from the depo until they have a period but that it can take up to a year for a period. I was wondering how that works since I am switching birth controls. With NuvaRing you are supposed to get a period on the fourth week. I am not sure how it will work since I still have depo in my system.