I'm sorry that you are in pain and don't have health insurance.
There really isn't any way to give you an idea of what is going on.
It sounds like you may have bruised yourself and don't remember doing it;
The pain with a full bladder could be pressure on your spine and a disc.
The swelling could be from bruising or a cyst.
Unfortunately, you really do need to see a doctor about this and see what a doctor thinks and advises.
If need be, especially with no insurance, you might want to consider a trip to the emergency room to be seen. They can't refuse to see you and give some kind of diagnosis and give you some kind of treatment.