Estrogen Treatment??

So I'm a bit confused about my doctors treatment plan for me. I have Mirena (in year 3) and my OB-GYN is having me take Lo Loestrin so I have estrogen too? It seems weird to me. I had my lapy/removal in January and started the additional BC at my post op appointment. I've never liked bc pills, I'm now breaking out like crazy and craving sweets even more than usual. Up until the last week, I'd been okay pain-wise, but lately I've been having shooting pains again. Tonight I had pain so bad I screamed and collapsed... my husband almost took me to the ER. Thankfully it lessened quickly and I'm alright now.