(((Sarah))) - Ok I'm going to duplicate here.

Do you think you might have a bladder infection starting?

Like Fin, I get the bladder spasms too. They feel similar to what you are describing but other times like a tight ball. Is is possible you are having bladder spasms?

I would certainly have them check your urine this coming Friday and also discuss this with them. Go in sooner if you get worse or it actually hurts to urinate as an infection will do.