My female dog is not conceiving at all

Question
QUESTION: Dear mam, I have 2 dogs, a male German Spitz and a female miniature spitz .... My male is 4 years old & is a proven male as he has fathered pups with another female dog... My female dog is 2 years old & has had 5 heat cycles till date ( once every 4 months ).. I bred her on the 4th and 5th heat cycles, but both the times she did not conceive ( I mated her with 2 different miniature spitz males and not with my male dog because of the size difference ).. First time, I feel that I mated her a little late , but second time everything was correct ( I mated her twice during the 5th heat, first time on the Monday when the vet said it was correct & again on Thursday,but she hasnt conceived )... My vet said that her uterus and fallopian tubes are all normal during a CT Scan and said that she did not conceive because I mated her only twice ... In addition to this, I feel that she behaves abnormally, coz during both the matings she refused the male dogs and was aggresive when they tried to mount her, she even sat down when they did so.. I had to hold her tight and force her to get the tie ...( But during her fourth heat, when the doctor said that she was in estrus, I left her with my male dog to see if she behaves same way to him also... Before me she acted like a playful thing not interested in breeding at all, but when I left and watched her through my window without her notice, I found her lifting her tail to my male dog and allowing him to sniff and lick those parts... But when he tried to mount her, she sat down.. The only change in behaviour was that she was not aggressive to him at all.. After this, I separated them & forced her to mate with the miniature spitz )

Do you think that if I had left them alone for a longer  whileshe would have mated with my male dog naturally ???

& why does she act before me as though she is so innocent ?? Are dogs shy of humans during mating.. Iv seen street dogs mate on the road itself .. Why is she alone behaving abnormally ???

& is it because of the forced matings that she did not conceive or could there be a problem with her or the male dogs ?? ( the vet said that her uterus and falliopian tubes are normal )

ANSWER: Hello,  I need a little more information.  What day did she go into heat and what day after that did you breed her.

She may not like the males or she just doesn't like being hurt.  It hurts the female to mate if she is not swollen enough.    That is why I am asking you about the days you bred her.

Can you get back to me on that?
nancy

---------- FOLLOW-UP ----------

QUESTION: Well mam, I actually mated her on the 10th day of heat during both the 4th and the 5th heat cycle ...

4th heat cycle : bleeding started on Feb 20th 2012, on feb 25th itself I saw the vagina swelling but as I had some work I could not breed her that week .. On Feb 27th, I gave her a bath and immediately after the bath her vagina shrunk ( I dont know if its got anything to do with the bath )& it never expanded again.. Then on Feb 29th( 10th day ) I tried mating her but as she did not cooperate I took her to the Veterinary college and got an ovulation test done... The doctor said that she was already in heat ..

5th heat cycle : This time she came into heat on July 14th 2012.. But this time her vagina did not swell on the 6th day like the last heat... But, not to commit any mistake I took her every 3 days to the vet to know the ideal period.. on July 23rd ( the 10th day )the vet said that it was the ideal time and I mated her that day itself and repeated a mating on July 26th and stopped.. 2 days before that is on Sep 1st 2012 ( 41st day ), when an ultra sound was done my vet said that she was not pregnant.... She has also asked us to bring her after 10 days mentioning some 'sperm viability' , which I could not understand , to rule out pregnancy ....
Moreover, on the 38th day after mating , my female dog had a voracious appetite for 2 days, that is on Aug 30th and 31st ... But ever since the veterinary visit, she is again back to her normal appetite...

NOTE : She has not been eating very well ever since the mating ( ofcourse, if I put chicken or any non-vegetarian food she gulps it up ) .. + not much behavioral or appetite changes, except that she has stopped eating rice ....

Answer
Hello,
Dogs are usually fertile the thirteenth day, so mating is usually on the eleventh and the thirteenth (this figures in the three days the sperm lives), so the tenth and twelfth day should have been fine.   Your dog needs extra nutrition to conceive.  Put her on a high beef or lamb diet prior to her next heat, or chicken if you have to.   I think she needs lamb or beef though.  Dogs are carnivores, in the wild when there is not enough food, a bitch will not come into heat, so a vegetarian diet may be keeping her from getting pregnant.   Make sure she is swollen the next time you breed her or she will experience pain and not want a dog near her.  I believe she has experienced a lot of pain and now is afraid to mate.  You can tease her with your male, but choose a different male mini spitz so she doesn't relate him to her painful experience.  
When I am breeding my bitches they get hamburger meat and some rice as well as a high protein dog food.  Try this and stay with your vet, she seems to know what he is doing.  Most vets haven't bred dogs a lot though, so I hope these tips help you out.
Also, make sure you have an area where she can go to have her puppies.  If she doesn't feel safe she can actually absorb the puppies back.  There may be another name for this, but all of us in the business call it that.  She needs to have a place of her own where your male cannot go.
Lastly, you need to relax, if you are tense about this whole situation, she will pick it up and be afraid.   Don't be in the room when you breed her next time.  Put her in a place where you can see her, but she cannot see you.
Let me know how it works out.
Nancy