It possible, but from what I understand one of the reasons mirena works is by thinning your uterine lining so an egg cannot implant-thus, minimal bleeding during your period. I have not had a good flow since removal, exactly like you described. my bloodwork confirmed I am in menopause.
I think when you ovulate you get some kind of discharge at that time. I used to get a cramp as well. I would recommend you get your lh, fsh, estrogen and progesterone levels tested. You must do the test ASAP after your period starts, otherwise the result are pretty much useless.
Youre still pretty early after removal, so don't panic about it yet.