Intact female have discharge for months

Just looking for some advice or to hear if anyone’s had something similar happen with their dog.

My dog’s heat cycles have been kind of all over the place. She had bleeding in October, again in February, and what seemed like a full heat in April with all the usual signs.

After that, she started getting a white discharge. We had an ultrasound done and the vet said everything looked okay at the time. It’s been going on for a 2 months now, and she’s also already had two rounds of antibiotics.

But over the last week it’s changed. there seems to be more of it, and it’s gone thicker and kind of pinkish/darker in colour.

She’s booked in to be spayed on the 15th.

Has anyone seen anything like this before? Just trying to figure out if this can still be hormonal stuff or if I should be pushing for another vet check before her surgery.

Any advice or experiences would really help.

She is 9 year old staffy/lab