Mirena IUD and Lo Loestrin Fe bc pill

So I got my Mirena IUD inserted in August 2017, since then I’ve had continuous bleeding. I have Hypothyroidism so I’m already tired as it is, the bleeding is only making it worse. I finally gave in and made an appointment with my ob/gyn to check it out. They prescribed me a birth control pack for one month and it is supposed to balance out my bleeding.. will that affect my Mirena ? Can it make it not effective? I’m just scared to have intercourse and get pregnant. 😒