Choc Labrador smell

Question
Why does my Labrador smell, and what I can do to help her.

Answer
The question is very vague, so my answer isn't going to be specific.

Dogs that do not smell "clean" either have rolled in something, are not doing well on the food they are being fed, possibly have anal gland issues, or if they spend alot of time wet, they could have a fungal issue growing in their coat.  

My recommendation, since I can't smell your dog personally, is try to make an immediate appointment with your vet when you think your dog is the stinkiest.  They might be able to identify the odor causing problem.