Whats wrong with my dog?

Our dog is really thirsty drinking tons of water, she was shaking really bad today like she was having a seizer or something, her hind leg is bothering her and her eyes are pretty pink and a lil bloodshot. she got a little bit of weed killer in her mouth about 5 days ago but i wouldnt think it would be enough to hurt her. she is a little foamy at the mouth and doesnt really want to get up much