I believe you are creating the open clubface as you start taking the club back at address. If you look down at your club as you start your takeaway you should see a clubface that is slightly closed to the path you're taking the club back on. A club face that points slightly to the right of the target and a back swing that at doesn't even think about going to the outside of that line is a good start.
As you proceed back you need not be afraid to let the face open.
It is important that you start the back swing as a proper swing motion. Use your feet, hips and shoulders and not only your arms to get the path right. No cheating. You want a glitchfree back swing that sets you up to come down the way you went back. You may have to adjust your shoulders and head position at address before you're set to do a square takeaway and a drawish downswing.
There are a components and component variations and component compensations that goes straight to the heart of doing the geometric motion that I described above. And there are several here on LBG who can help you with the finer details of all components involved. I hope some of them will chime in, because your situation is very common.
And there are many possible paths to lasting improvements. A teaching pro might choose to address the symptoms directly or rebuild to a better stroke piece by piece. In which case you should go with the pro.
Being picky about the address and takeaway never hurts in any case, IMO.