GH is totally correct. Basically the issues you are experiencing are the welcome mat to learning white water control. Creekers are less edgy, and that is MUCH to your advantage at this stage (especially if you continue to learn in moving water.) As mentioned by GH, get on a lake and don't worry about moving water until you roll is totally perfected. That way when you do flip... you can roll right back.
In regards to turning your boat it's all about edge control and how to utilize your hips correctly to compensate for what the water wants to do. This will ONLY come with time on the water. Indoor pool sessions are the best way to get that kinda time during the winter.
It will come in time, but yes, kayaking isn't easy.