Hello, Diana and welcome.
My name is ***** ***** I will be glad to assist you and Suzy.
If she is not spayed, the milky discharge can be due to a serious uterine infection called pyometra, which must be treated by a vet, right away.
Is there any possibility she's pregnant?
If she's spayed, the milky discharge and spasms that look like contractions are not normal and still need to be checked out by a vet, asap. If your vet doesn't have emergency hours, bring her to your nearest ER vet, now, to get a diagnosis and treatment. Unfortunately, there's nothing you can do at home for these symptoms.
I hope all will be well with Suzy and please let me know how she's doing and what the vet's findings are. Thanks!
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