Very creative photo. Expression is good, exposure is good.
Composition: this is where you could have scored better. As your commentors have mentioned, the foreground detracts from the image. I would remove all of the out of focus foreground and leave enough of the rug to frame his face.
The image as a whole needs some sharpening. I would start with the face and allow the focus to go towards his face by making it sharper in contrast to the out of focus background. This will allow his face to pop a bit more and stand out.
Might even desat the brown in the background a bit so it does not detract from that face. Use of levels and brite/contrast on face only would help as well
Such an emotional expression! :) A little bit of catchlight in the eyes would boost this some. However, you did a nice job of handling the backlit environment in this. Good luck.
Awww :-) I love Bulldogs; they have the best personalities. I think I would crop this much tighter on the bottom, as the OOF ground isn't adding much IMO.