Sarah, sorry to hear your having this problem

I get this from time to time, and from my tests with the urologist - my bladder spasms. The more empty it is, the more it spasms.

They also advised kegels for this, and it has helped a little bit for me. It still has a tendancy to go wonky when it's hot and humid out.

I might call the doc if it keeps getting worse just to make sure everything's ok. Hope you feel better soon.