I have had my dog for 6 years and she is acting out lately. I left for a month and when I returned she stared pacing and crying at night. She was never alone while I was gone but she acts like she was alone. She has a brother that is acting fine. Also I don't know if this helps but I have been seriously depressed lately and was wondering if this had to do with anything. Please help!

Yes, I would guess that your going away AND being depressed have affected her.
Not all dogs are as sensitive as others.
Give her lots of love. When I'm depressed holding my animals and talking to them does wonders for me.

Sometimes dogs do that as a pain response, anxiety (Not separation anxiety, just regular ol anxiety) or seizures.

Since this is happening frequently, you should probably get her checked out by a vet to rule out anything major, such as seizures or pain.

Healthy dogs do not walk around the house whining... This shouldn't be ignored. Seizures are not always the grand mal, laying on the floor convulsing... they can be minor and the dog will just act agitated and they WILL be clingy and extra needy.