Im sorry you have to go through all the questioning
on here ...some people just want all the "right" answers.
Im sure that if anything were amiss the vet would have found
it by now. Being a woman myself, I have abnormal periods,
and its no surprise a dog may as well.
My dog was 10 months old before she had her first heat,
and the next one came 9 months later, just before she
got spayed. The vet also found nothing abnormal, and
said it is common for some female dogs, just like women
to have abnormal cycles.
Good luck! Im sure everything will be just fine!