This was a classic perception vs reality issue for me. I always felt I was keeping level but shockingly I was lifting quite a bit. It helps if you can get a video camera to take your swing. I changed my perception to feel as if I am going slightly down in my backswing, video showed that I was then keeping level. (I made sure I taped it well so that I was not over stooping instead). After a while perception has merged with reality - I now feel level and video shows I am indeed level.

So get your swing taped if you can. It will show up other faults you might not even perceive at all Cheers.