2001 Chevy Lumina over heating

Little old lady here with a poor old Lumina. It is overheating. Started out wouuld overheat when at a stop light or idleing but would cool down driving in traffic, etc. I would fill up the overflow tank every couple of weeks. Now it is overheating in just a few blocks and doesn't cool down at all when driving, even at highway speeds. Last time I drove it it reached the red line on the temp gauge. I have to put water in every time I drive. Takes maybe a gallon. I don't think the dual fans are working. When I check them while car is running they don't turn on at all. If I turn the air on while running one fan, driver's side, will kick on after a few minutes. Also, the two burp ports I opened to see if water would come out while I'm filling the radiator, the one on the passenger side lets water out but not the one on the other side. I put stop leak in the radiator, thinking that might help, it acutally got worse after I did this. Can you tell me how to check if the fans are getting power, and how do you flush a radiator? It appears there might be a blockage in the radiator itself or in some water line? The water pump is working. And lately the over flow tank isn't emptying into the radiator like it should. When the radiator takes about a gallon to fill, the over flow tank is only down a couple of inches. Please help. I am on a fixed income and disabled and can't afford to take my car to a shop or even to hire a mechanic after hours.