You're asking us if you could be pregnant? Any of the Big Box stores has a pregnancy test for around ten dollars. Go buy one and check. The tender breasts COULD be because your body is recovering from the removal of the coil. PS for the baby's sake, marry the partner. It's not just a piece of paper, it's a covenant that creates a permanent bond.
Mirena can cause spotting and other irregular and heavy bleeding in most
common in the first three to six months after insertion, after six months ,
the number of bleeding days, usually decreases and bleeding starts to regulate.Irregular bleeding patterns may continue beyond six months in
some individiduals.
Women who do not menstruate within six weeks of their last menstruation
should see a doctor to rule out pregnancy.
As you had mention tender and sore this may have been from having the
Mirena coil out then there's always that chance pregnancy could of occured.
Suggestion, you should follow up with health care provider.