Q: overheating problems

I have had overheating problems shortly after i bought my 2001 pontiac sunand had to replace the head, water pump and thermostat. It ran fine after that for awhile and then it overheated on me twice randomly. The coolant wasn't completely gone but after i topped it off it drove fine. My dad put stop leak in it and then i couldn't drive it but a few miles without it overheating. We replace thw thermostat and flushed water through the radiator hose. We did that and it fixed it for a week or so. I had to put 3 things of coolant in it since we flushed it no more than 2 weeks ago. Then it start3d running hotter, around 220 degrees but not overheating. Its burned through coolant but as long as its full it runs without overheating but i have to stop and fill it up with coolant so often i started putting water in it cause the cost. I filled it with water twice and checked the levels after i drove it to see how much water was used and now theres coolant in the resevoir!! What is going on?