PCS is Pelvic Congestion Syndrome otherwise known as PVFD (Pelvic Venous Flow Disorder).
Basically, what this means is there are varicose veins within my pelvic area. They can be adjacent to your ovaries, uterus, Fallopian tubes or just be in your pelvic floor. Over the course of the day these veins fill with blood and cause pain.
If you’d like to learn more about what PCS is I like these sites for education: