Min Pin and her heat

Question
Sorry to bother you, if you cannot or do not know thank you for trying to answer.  My question is I have a min pin that is four years old, she is very special to me, and I would like to have one of her offspring.   She has never actually went into heat. She has had about 1 day of swelling, but never the full heat.  Her vet says she is still healthy, but he says that she must be in heat longer than that but I am not noticing.  So is there any other ways to tell?  She is kept inside (puppy pad trained only walks to the park, but she is always on a leash and doesn't try to run away), and she hasn't bled that I know of.  The only visible sign I have noticed is swelling, but as said earlier it only lasts for about a day.  If there are no other signs should I still try to bred her when I see the swelling?  If you could please help me I would greatly appreciate it, thank you very much.

Answer
Hi Michelle

Small dogs are harder to detect.  But dogs that spend a large portion of their times indoor occasionally don't come into season as regularly or as long.  In large part because of the the amount of time they spend in natural day light.

What I would do is have her thyroid levels tested and place her on vitamins and oils.  This will help kick start her system.  

You can try and breed her when you see the swelling, what you need to do is introduce a experienced male to her.  He will let you know for certain when she is ready.   Also progesterone testing is a simple test done by drawing blood. It can tell you her levels and when she is about to ovulate or if she has already.

Good luck.