Hello Tricia,
If the shed is off by very much, I would suspect that the levelness of the lamms needs to be checked by putting the locking pins back in.
If you have a bad shed due to the treadles colliding with the lamms, your treadles are probably too high (or too close to the lamms, which is one of the most common problems, and happens when you start tightening cords too much). Your goal is to have your shed in the center of the reed, which could help advise you on whether to raise shafts or lower them. Your beater is of course adjustable, so if you have a good shed but it's not centered in the reed that will reduce the size of your shed, which can be easily fixed by adjusting the height of the beater. My guess is that your issue is a combination of the lamms being too low (saggy), and/or your treadles are too high.
Good luck, and let us know how it goes,
Becky