I take ortho-tri lo, and didnt your doctor or whoever you got it from tell you when you can switch? It depends if your on the anyday start or the sunday start. Sunday start you have to wait till the first sunday after your period starts, (if your period starts on a sunday then you take it on that day) an anyday start you can do anyday as far as I know, but im on the sunday start. :)

I hated othro evera! I have been on the shot of and on for 7 years, and I love it. The shot u only get it for 4 times out of the year. The shot helps get rid of bad menstral cramps and symptoms u may have when starting ur period. Also in my case I had a period once every 3 months and it was good instead of having it every month. My sister also loves the shot because she never had a period, it depends on ur body, but orthro evera I would not even recomend that to anyone. :)