Lab spayed, now urinating frequently.?

I'm hoping that this will have a straightforward answer! My 7 month lab was spayed 2 days ago and after being a bit groggy on the day we brought her home she has been rcovering well, back to her old self really. However I noticed this morning that when she goes out to pee, she is doing quite a long one, followed by not being able to come back in without trying to squeeze a few more drops out up to 5 times more. It's like she wanders round the garden squatting again and again. It's most unlike her. Is this just post-operative discomfort, or something more sinister? All advice valued!