Can't perform a kegel without tightening my butt

When I perform kegels, my buttocks squeeze. I can see my penis still moves and I think it’s working, but is there a problem with this? Am I doing something wrong? I do what you’re supposed to do to prevent yourself from peeing, but my butt always tightens.

I find kegeling with an erection helps me differentiate between the different muscles. I try and focus on the muscles that make my penis rise, while excluding the rear muscles that wrap around the anus area

There is nothing wrong with that. What is the worst that can happen, you get a tight butt? The main point is you are still getting a kegel workout.