A bulky uterus , backache , heavy bleeding, and pain are all possible symptoms of fibroids, I had a very bulky uterus
that contained 16 fibroids and one of
which was larger than the size of
an average uterus on its own! , you can see why this would cause pain as it would be pressing on other structures in the pelvis.
I hope you get the answers after your scan , please let us know how you get on and good luck.