Hi! I Was Put On Mimvey In Place Of Prempro.

Hi! I was put on Mimvey in place of Prempro. I was taking a low dose of Prempro and the Mimvey is 1/.5...I was taking a held pill of Zmimvey and decided to try a whole pill...I started bleeding...should I go back to Prempro? No side affects with Prempro...thanks