Is there a reason she is not fixed yet? Were you planning to breed her? Very possible as Pen said, she had a cycle and you missed it, kept herself very clean...or had a silent heat. If, she indeed, has never had a cyle, then she needs spayed and not used for breeding.
i already talked to my vet regarding this matter, she said that my dog hasnt come into heat yet she advised me to give her vitamin e supplement....i noticed her vulva had been swollen for days but theres no blood....im planning to breed her......
From the experience of a breeder - dogs who don't cycle normally also tend to be a lot more prone to having difficulties in their pregnancy and whelping. It's often a hormone inbalance that causes this - which makes carrying a normal, healthy litter harder. The one girl that I had who had silent heats and didn't cycle regularly also required a c-section for the one litter I bred from her because her she never had normal contractions. I'd be prepared if you decide to breed her to have to do a c-section.
Get your hands on every book you can on whelping puppies and find a mentor (someone who breeds Yorkie's). Unless your vet breeds dog I wouldn't rely on them as a good source of information. As a breeder myself, I haven't yet run into a vet who knows as much as I do about breeding - and especially not about breeding MY breed. Don't rely on your vet to hold your hand and tell you how things work.
You need to really sit and think about whether you're prepared to breed you dog. The less you know about breeding and whelping puppies, the higher the risk is for her. Female dogs DO die from complications in whelping - it doesn't happen a lot, but is MUCH more common when they "breeder" is a novice and doesn't know what they are doing.
Especially with a toy breed you need to make sure you know what you're getting yourself into. The puppies are born VERY small (2-3 ounces) and the first several days you have to be careful that they don't have issues with hypoglycemia and stay warm. It is NOT all fun and games. Not every female dog knows what SHE is supposed to do - and pet females are more likely to lack maternal instincts. Are you prepared to act as a surrogate mother to puppies? To tube feed or bottle feed a weak puppy or the whole litter round the clock, every hour, for a week?
Why do you want to breed your female? That's the biggest question. Ask yourself if all the possible heartache you may encounter is worth the "reward" you're hoping to get.
i did already breed my dobe and i can say i already have some knowledge in breeding....i read threads in forums about breeding so that everything i have to know about breeding my dog and also some tips from the expert breeders......i really want to breed dogs currently i already have 6 dogs at home......im really having a hard time on my tzu wether her cycle is normal......thats why i'm asking you guys to help me or maybe some tips.......
In my personl experience, a female who cycles this late, silent heats, irregular cycles also has problems with conception. If you are ever succesful with conception, they tend to only have one or 2 pups, have whelping troubles, isue with puppie thriving, etc.
I would suggest consulting with a vet who specializes in reproduction. They have more knowledge, access to test and more ways to assist you in your questions than the average vet.
I have yet, or know anyone who has had good outcomes with breeding irregular cycling female :(