There could be many things going on to cause him to look at you. I find most often it is from concern. Could be he is uncomfortable with the distance from you, could be he uses your position to clue him on flanks and is not certain without that, could be being off balance worries him...
I would step back and move into a smaller space or start again in a smaller space to rule potential problems. Get his stops and off balance flanks comfortable without you "helping', moving, patting your leg ect. Do it in a manner that training is enjoyable. Many folks train like they want it in a trial - they ask for straight lines and slow pace to soon. YOU have to get the dog enjoying himself, wanting to work understanding the commands first THEN slower and straighter. When dogs are keen and wanting to work then you can correct. If you correct while they are concerned often that causes more concern. Dont worry about lines or speed, allow him to go faster without harm to sheep. Get his stops and flanks and off balance then try straight.
He is telling you he is not comfortable/ does not understand when he looks at you so dont make him tell you that. Be there to encourage him and shorten it up, small pieces, little off balance flanks ect. Get him keen and happily working then stretch it out. SSHHH or other sounds will work, dont worry about perfection now. Use your sheep more, faster lighter sheep may be needed.
One thing I have done is fade in and out of view when my young dogs are learning to drive. So sheep in front dog behind at a nice distance from sheep and me off to the side quite a bit between sheep and dog. So three points to a lopsided triangle. We all walk forward, then I walk slower let the dog push sheep forward so I am to the side a few step back. If I see the dog starting to be concerned I walk faster drift back into view. That way the dog does not look back for me. As he gains confidence I drift farther out of sight, and further to the side. I also work from both sides of the dog. I can start driving in a square around me then lengthen it and remove myself from the picture slowly. IF you are more to the side it seems to gives them confidence and not teach them to look back wondering where you are.
Some dogs I use a long line to help them flank and drive because that allows me to Help Without correction. I do not want to Need to correct a dog when learning to drive because it seems they translate that into I am not supposed to be in front taking sheep away. You need to keep moving and staying on the hip of the sheep so he does not turn things into a fetch when you ask for a flank till he gets comfortable with small flanks and walk ups.
Hopefully you can picture that, if I need to explain it differently let me know.