My 8 month old puppy is acting very lethargic, walking slow and seems to have some weakness in back legs when trying to stand from a laying or sitting position. He still has a little appetite and drinks some water. He got into some leakage from our septic tank a couple of days ago, but we had not put any chemicals in it. I believe he did eat some feces. Could he be sick or have some kind of injury? I will be taking him to vet in the am. He is a beagle/hound mix. He just seems to have very little energy right now. Could he be depressed or could worms cause this? He is up to date on shots.