Pauzel thank you for your question!
I am sorry to hear about losing your ability to drive the ball like you used to and the lack of confidence, let#%92s see if we can look at few things to get you back on your game.
First, Randy Smith makes some strong points in his article this week by making adjustments in our grip to help our ball striking and shape. Let#%92s be sure that your grip is not too strong. If you are a right handed player I always like to see two knuckles on left hand while gripping the club and the right hand in a neutral position sitting comfortably on top of the left thumb. Also, make sure you don#%92t see too much of your fingers on your right hand, this is a sign that you could be getting to strong again. Work on feeling neutral or a bit weak and create a “seam” as Randy Smith calls it with the right index finger and thumb. You can place a tee in the seam to work on grip pressure and keeping it in the right position.

Next, you mentioned that you felt flat or very round in the swing rather than up and down. That#%92s not such a bad thing as long as you are not getting the club well inside on the backswing or getting laid off at the top, then it can be a can be a big problem. If you do feel a bit inside and round, try feeling the first move a little to the outside so you can be sure to begin with club in front of you. It#%92s surprising how odd that can feel for players who really whip that club inside, but it can pop you right back on plane.
I have mentioned the “woosh” drill many times and it can aid in an early release of the club causing the club face to close early resulting in a hook. Try the drill it really works and provides tremendous feel for a late release and proper acceleration. There is another post within the forum talking about this drill and a case of the snap hooks that you need to check out. http://www.tees2greens.com/forum/Topic398-28-1.aspx
I would love to see your swing if you can give me a link to it or embed a video in the post. I am curious about the swing plane most of all. I hope some of these tips will help straighten you out and always if you have any more questions or comments please post them. Good Luck!