Feels like I need to pee during sex...

The last week or two, I will suddenly feel the urgent need to pee during sex. I haven't experience it before.

I've been making sure to pee beforehand but I still have been getting the feeling. It was so bad that last night I suddenly yelled "STOP!" to my poor husband who confusedly stopped and just sat back. I was too embarrassed to tell him I was freakin afraid I was about to pee on him!

And it's not the build up to an orgasm, because I know that feeling.

So what the heck! Any ideas?