Maybe Pregnant

I might have a problem although I feel like is not a big deal and I might be over reacting. I'm on the Nuva Ring Birth control method and a month ago I spotted. I did not have a regular period. Since I went on the Nuva ring my period is about 3 to 4 days long. This time is was 2 days and it was spotty. I took a pregnancy test and it came out negative. But I heard that it takes a while for the birth control to clear out of your symptoms so it won't show if you are pregnant or not. Idk what to do . I gained crazy weight since then and get all these crazy cravings