Every time recently, when I get on top before any kind of penitration happens just kind of fourplay, I feel like I have to pee. I go pee and try again and it happens again and again. What could be wrong.

I suspect that the nerves that tell your brain that there is urine wanting to get out of your urethra are irritated for some reason having nothing to do with how much urine is in there.
That reason could be from something you did during sex that affected the tender tissues around the urethra, or it could possibly be the beginning of a UTI. If it starts hurting more, especially when you pee, see a doctor.
It could also be that something further into your abdomen is hitting/pinching that nerve or nerves too, such as an inverted uterus, or just all your organs sagging a bit, and pressing on nerves and each other, or a cyst. You may want to get an ultrasound if this persists. But this is something most women deal with in countless ways, especially as we age, or have children.

The fact that it only feels this way when you are on top makes me think it's not a UTI, so just try different ways of having sex for a while, and keep track of what happens in what position. But it's possible that the cause may never be seen on any test. Many times women have to work on exercise to solve such issues, and they do often get relief by strengthening their abdominal muscles.

Knowing how old you are would probably give a more qualified answer, but usually it is called urinary incontinence. Do you usually have leakage from time to time anyway ?

I am 72 now, but at 60, jogging, working out, always gave some leakage problems until I had a bladder elevation which solved that indefinitely. Not as extreme solution as one might think if one wants to be active forever without embarrassing moments.