switched birth controls, could i be pregnant?

I was on the nuva ring for almost a year and in feb i switched to the pill where you only get your period once every three months. when you start the pill you start it on sun after the first of your period, which i did. Now its april, and i feel different. i gained weight, i have new stretch marks on my breasts, when i pee it smells, like a really high ph level. i am only a little moody although i seem to get mad faster than normal. i did two HPT and both were big fat negatives. is there a chance that i could be pregnant or is it because i switched birth control methods???