How to treat crossed eyes to help achieve a better focus in vision?

Hello doctor,

I am a 19-year-old male, and I just have a quick question about my vision. Currently, I am taking two medications, Mydayis and Mirtazapine. They are not the problem because I had this issue for as long as I can remember, long before I started taking any medications. I have been to an optometrist, and from what I understood is, I have perfect vision. My problem is that they found that I could not cross my eyes. I have never been able to work on it for a while, not long enough for improvement. Whenever I bounce a ping pong ball on a paddle up and down, over and over, my vision slowly gets blurrier; even the ball and paddle can get pretty blurry, almost like they stop focusing on anything. When I stop, it goes back to normal. I could not find anything online, so I do not know if that is a normal thing or not, and I just wanted to check and make sure it is not anything I should look further into or try to improve on so that my eyes can focus better.