My Girlfriend And I Are Into Spanking For Fun. I

My girlfriend and I are into spanking for fun. I sometimes enjoy the pain of it so we took it a little too far with a paddle. There was blood in my urine today after a paddling that resulted in swelling and bruising of my buttocks. Only my butt was hit. This happened 2 times a few years ago so I now know it wasn't just a coincidence. Those are the only times I've had blood in my urine, after a hard spanking. I looked it up this time and now I'm worried it could be rhabdomyolysis.
We will definitely be playing more lightly from now on. But is there anything less severe than rhabdomyolysis that this might be? I only urinated blood 3 times then it has been normal the rest of the day. The first time the urine was dark brownish.