I had this scenario 4 years ago with my son. We had to move due to a divorce, and my kids (6th and 9th grade at the time) were traumatized by the thought of it alone. My son, particularly. He has a hard time making friends, and absolutely hates change of any kind. He also has a nervous stomache, and tends to manifest his fear and anxiety that way.
After many head-butting sessions with him, I explained that we simply had to move...no way around it. I then found that the best help for him was to keep the lines of communication wide open. I validated his fear, his concern, his disliking for having to make a change. They need to know that their concerns are being heard and taken to heart. I then made him a part of the transition...going with to the new school to be registered, driving around the town and finding things of interest for him, showing him all of the positives of our new location. When it came time to actually start the new school, I listened to all of his experiences each day. If he was down, we talked about that tomorrow would be better. If he had a scenario he didn't like, we talked about how he could respond differently next time. I also kept him looking at the big picture...that he wasn't the only kid who had ever had to move. Keep it in perspective. We all know that as teenagers, it's easy to make a mountain out of a molehill, and as a parent I can't become a part of the mountain. I have to be objective, and help him to be objective also.
All that said, my son DID adjust! In fact, he did way better than I ever would've imagined. He actually ended up liking our new location BETTER! He is now a Senior in high school, captain of the cross-country team, ranked #6 in his class, and extremely social. For him, the move was life changing in a positive way, despite his fear and anxiety at the outset.
I have no doubt that you will be able to facilitate a positive change environment for your son. Just remember that you're the role model, you're objective, and you're his safety net when he has concerns.
Lastly, I would still say to keep an eye on his tummy
If it becomes a pattern, then obviously you need to speak with your doctor or a counselor. Hopefully, you will be able to ease his concerns and the transition will be a good one. Let us know how it goes!