Q: Truck keeps overheating even after replacing thermostat.

I recently replaced the radiator in my 2002 Dodge dakota 4.7l because it was cracked. Shortly after replacing it the truck began to over heat. First thing I did was change out my thermostat and lower hose because it bulged up and was now soft. But still after that. It gets hot and overheats. Before it was when I was stopped at a light but now it'll do it while I'm just driving. I changed my radiator cap as well.But now the hose bulges up because it's soft again and my overflow fills up. I have to pull the cap to let the fluid run back in.If not it just keeps filling the overflow tank. I've ran the truck with the cap off and only tiny bubbles were emerging so I don't think there's an air pocket.I'm just not sure if it could be the waterpump or what.But it'll be normal temp for about 20 miles then get hot and I have to let it cool,Fill the system with the overflow, then it's good for another 20. Worked just fine before I replaced radiator. Hoping that's not the problem. It was brand new.

My car has 164000 miles.
My car has an automatic transmission.