Why is my pee frothy?

Kidney issues? Frothy urine is the text book description of a kidney condition called nephrotic syndrome where you spill a lot of protein into your urine. But "frothy" is a subjective term and your urine needs to be properly evaluated in person.
Maybe protein. There are a few reasons for "bubbles in your urine". The most concerning one would be too much protein coming from the kidney. If you think this is getting worse, then you should have a simple urine test and office visit.