Talk to your vet about using a different flea and tick medicine as others have suggested.
For keeping ticks out of your yard:
Clear any underbrush and keep the yard as tidy as possible. The less places for them and rodents to hide, the less their should be.
A three foot wide barrier of gravel around your yard can help keep them out of your yard. The reasoning for this is that they dehydrate very quickly and can't make it across that far of a surface without being killed by dehydration or exposure. If you live in a wet area, I'm not sure how effective it is.
Try using tick tunes. You basically place them around your yard where your dog can not get to them (they are poisonous to dogs). Mice and other rodents will come and take the filling to use for their nests and it will kill the ticks on them. This breaks the life cycle and reduces the population. You can also create your own tubes with toilet paper rolls, Cotten balls, and chrysanthemum oil. (Again, poisonous to dogs so keep it away from them). Putting them outside your fence can be a good idea and should be just as effective as them being in your yard.
A few friends recommended tick tubes to me. They said it made a noticeable difference in their yards. It might only be worth it for smaller yards though.