Can a microchip tell how many previous owners a dog has had.Ive just bought a dog,i have his microchip deatils but the person i bought him from seems clueless about any details of him as a puppy even though he told me he has had him from 9 weeks old but without going in to too much detail on checking his pedigree when i returned home( and i travelled a long distance for this boy) theres now doubts about his pedigree) so..can his chip tell me if im only hos second owner?

Unless whoever you got him from bred him you would be at least the 3rd owner.
The breeder should be registered as 1st owner.

wouldn't you be able to trace his breeder from mykc or similar ?

IT would depend on the age of the dog. The law in regard to the breeder being registered as the first owner on the chip is a relatively new one (I think April '16 in Scotland) and around that time for the rest of the U.K.

I'm not sure on this but I don't think they keep details of previous owners except the breeder and if they do, it might fall under the Data Protection Act so might not be able to tell you.  Can you ring the chip company and ask?  Different companies could have different systems as well.