3yrs. old female shih tzu Pregnant

Question
I have a 3yr. old female and a 15mon. old male shih Tzu. they have mated twice. the first time they didn't tie, the 2nd time they tied 4 times for eleven min. it has been 3 weeks and I can't tell if she is or not.   Could one of them be infertile?

Answer
Check her vulva to see if it is still swollen, also the first signs at this stage are usually increase or decrease in appetite - sleepiness - attitude change.  Is this her first pregnancy?
You really won't be able to tell for another couple of weeks her teets will develop more and then her belly will grow.  A lot of time they have been known to even loose weight at first because of the decrease in appetite and this is why you think they are not pregnant and the only real way of knowing is the swollen vulva, the change in attitude and the laying around and sleeping all the time (maybe even being sick).  Let me know anything you have noticed about the female since the tie ..  A tie by the way is when they lock up rear to rear and don't come apart at all for a period of time usually up to 15-20mins (one tie) So did they tie 4 times for 11 min each or did they just mount up 4 times in 11 min?  Get back with me, I can help further.