Your body has experienced trauma from the surgery.Your throat should feel better in a week or two.
I was gagging on my food and drink for about a week. It has taken about 6 months to really get my voice back and it is still getting stronger. It will get better.
I will assume you had anterior fusion? When they go in the front, they actually move the windpipe and esophagus to the side to get to the spine. It's no wonder our throats hurt. I had trouble swallowing for a long time. Take very small bites of soft foods, yoghurt, mashed potatos, milkshakes, jello. You get the idea. If your pills just won't go down, crush them if you can, stir into applesauce, and take them that way. And also avoid hot foods and drinks. The nerve endings are "asleep" right now, so you can burn your throat and not know it.
I hope you are recovering well. It's tough to get thru, but how wonderful that dr's can do this now. Imagine 150 years ago! My prayers are with you.