My dog was sterilized beginning of the year?

How do you know she's in "heat"? If she is just humping or letting another dog attempt to hump that's not being in heat, that's just how dogs try to dominate each other. If she has any type of bleeding you need to have her seen by a vet ASAP...this is not normal. I would call the vet that spayed her just in case and share your concerns to verify they actually did the procedure and if they did there's no way she can be in heat because most vets perform a total hysterectomy (OHE) and there are no female organs left for breeding. If a Tubal ligation was performed (most do not do this) get your dog to another vet and have the OHE done.

If your dog was spayed this would be impossible. A dog receives a hysterectomy, a complete removal of her uterus and fallopian tubes, therefore completely eliminating her heat cycles. A spayed dog does not and never will come into heat.

Therefore, what makes you think this dog is in heat? Call your vet, if your vet spayed your dog they need to be sued for medical malpractice. Discuss this with them, your dog needs a vet this is not normal.

IF there is no discharge and you think she is in heat due to males being attracted to her, then it is probably a urinary tract infection. When they get UTI's they let out a scent similar to the sent from estrous. I wouldn't jump into malpractice but call your vet and ask about your situation. Most vets are very reasonable.

If she was properly sterilized then a heat cycle would be impossible! she could have an infection why not seek a vet advise.

No not normal - in fact impossible.

If she was spayed then this must be a UTI or something worse.

You need to get this checked out.

Not possible. Something is wrong and you should have her checked by the vet.