About three weeks ago I notice big flies in the apt. once I got rid of them, I notice more were coming. Now I its cold in ga, so I have no doors or windows open at all. After I got rid of those I keep seeing them, but I have no idea where they are coming from. There like big blow flies. Can some one help me out?

Blowflies (calliphorids) feed on decomposing organic matter, such as carrion, food waste and sewage. The flies may have been feeding on a dead mouse or worse in your sub area, basement, wall, attics, or air ducts and getting into the house through the vents, window wells, wall outlets, or plumbing. Have there been any bad smells? Have you found where the flies are getting into the house? Do you have a dog, or livestock, living with you or nearby?

Blowfly eggs hatch into maggots that feed on dead things. Blowfly maggots get ready to become flies by crawling away from their dead host to pupate, and emerge later as winged adult flies.

By now, apparently six weeks since you first starting seeing the flies, you are, hopefully, seeing a decrease in the number of flies, or the problem became serious and you had to seek professional help.
Univ of Nebraska - Blowflies in the Home

If an odor or the flies persist and you can't find the offending corpus delicti, you might have to hire help. Most pest control companies should recognize a general category of "garbage" flies and help you with a solution. Seek the assistance of a local farm adviser, or agricultural agent to ID your fly to species. You could have a stable fly, house fly, blow fly, bottle fly, etc. Proper ID will allow you to determine what the fly is feeding on, and get you closer to getting rid of the problem.
UCIPM - Flies

In the state of Georgia, it's entirely possible you have an infestation of Cluster flies in your attic. They are also big and slow and more often seen in the Winter.
Cluster Flies — Entomology — Penn State University