Hi Christine. Welcome to the board. I'm Dawn, the community leader for the board and a sahm of two.
My 9 yo was also a kid who insisted on being near me all the time. He was very reluctant to try anything unless I was there. I was late in signing him up for preschool because it was so bad that I could not imagine him doing well in that enviornoment. Something happened though about a month after he turned four. He started asking when he would be going to school and what he would do there. I found a program locally that was 2 days a week for a couple of hours. All the kids in his class went those 2 days and for the same amount of time, because I knew he'd have an easier time that way. Routine, knowing what to expect each day helped a lot with his anxiety about being away from me.
A few things that also helped was taking mommy and me classes together. I told him that when he was a bit older he would get to take those classes without me and I would love it if he'd show me what he learned. I kept it matter-of-fact and that was just the way things worked. I tried very hard not to let on that I was nervous about how he'd do. I also got some workbooks (more like coloring books) for him to do at home with me and we checked out some books from the library about starting school and what to expect.