My sister and I live together and she has been out of town for the last month and I have been caring for Max, her black lab. Just yesterday he started following me around more than usual and being restless and occasionally making a small whining noise.
I then noticed that he had not drank any water out of his dish and by late evening had not eaten any food. Since she has been gone his eating times have been off but he is always drinking water.
When I tried to get some sleep last night he would pace, then lie down for a minute-get back up pace some more. He did this over and over again all night. I finally noticed that when he would lay down is when he would do the whine-like he was possible injured or something-but nothing has happened to him where he would sustain an injury. Nonetheless I still did a quick check of all his legs-and did not notice anything off.
He would also stare off at nothing and kind of walk sideways to me(he never has done this before)
I am not a dog person so I have no clue what could be the problem. Is he just now becoming depressed due to my sisters absence?
Please help!

Calling her vet is a really good idea. Explain his symptoms and I'm sure they'll take it from there.

He could be depressed. My dog will often whine and not sleep well if either my husband or myself is away. HOWEVER, if you are concerned I would call the vet and have him checked out. As a dog owner, if the person I had taking care of my dog took him to the vet because they were concerned that he was ill I would happily pay the bill!

luvmotox, it really sounds like he needs to be seen by a vet, walking sideways and whining when lying down are both signals to me there is something wrong.

The not drinking is a serious symptom. Try to get him to the vet today.