Please take a look at my photo gallery and let me know what you think.
I'm afraid that I think your puppy is of mixed breed. For the exact reasons that I think the OP's puppy IS purebred, I think that yours is not.
The photos you have in your gallery are quite small and a bit blurry, so it's not that easy to be definitive... However, based on what you've got uploaded, I would not have any confidence that your pup is a purebred boxer. It is not because the length of muzzle is a lot longer than either the American or FCI breed standards describe (which are actually just different descriptions of identical proportions), per se, but because of it's shape. It would be interesting to see a larger photo, and how he develops. But I can see no sign of the square, undershot jaw of a boxer (is she undershot at all?). This pup appears to have the scissor bite of a hound - which is the exact opposite one would expect to see. That, along with the missing mask, and tapering head ARE some of the usual giveaways that the pup is probably a mix (and that are all absent in the OPs case).
Not everyone who asks that question really wants an answer - so I would add that it does not change the fact that he is a fantastic puppy

You should in no way take the above as a slight, or even remote suggestion that he's inferior. It is neither.