My son suffers from depression and anxiety. His symptoms started with stomach upset, and escalated into suicidal thoughts - to the point where I had to hospitalize him. I believe that it was triggered by a number of very stressful things we had going on in our lives at the time. Oh, he had just turned 14.
One the one hand, knowing the trigger is helpful, but not necessary. Our stressors are greatly reduced, and J still deals with anxiety, a year and a half later. The depression is better, though we have been reluctant to decrease his meds, so it's hard to know if it's better, or under control.
Getting your son checked for physical causes is certainly called for.
The anxiety about his illness - with the added stress of school starting soon? - is enough to get him into counselling, IMO. I know you asked him about it, but his reluctance may be caused by several things: he might feel that there's a stigma attached to seeing a therapist; he doesn't know what to expect, and can't see how it would help; he doesn't understand the connection between his physical health and his emotional state.
My son has been in therapy (off and on) for 18 months. DH or I attended most of his sessions with him. At first, when asked how he felt about something, his response was "I don't know". Pretty soon he was able to identify, then articulate his feelings. He continues to get better at this.
It also took time for him to trust his therapist enough to tell her what he was really thinking. He doesn't warm up to people quickly. But once he reached that stage, things really started to take off for him.
The nice thing about going with him to therapy is that I could describe an event, tell how I handled it, and get feedback from the professional. I guess I have pretty good instincts, because she usually agreed with what I did. Hearing her say that helped J to trust my instincts as well, which made things easier for us at home (I don't know how may times I said "I'm not a professional, but this is what feels right to me").
He was doing great last winter, than backslid a bit in the spring (more anxiety than depression). But he keeps talking to me and DH, and seeing his therapist when he feels like he needs to (before a potentially stressful event, usually). He has developed some pretty effective tools for controlling his emotions, and making the distinction between what his emotional brain is telling him, and what his logical brain knows.
Hugs, Kathy! I know how hard it is to watch a kid be sick - all you want to do is make it better, and there's not much you can do. I really think you should get your doctor to refer you to a good therapist who works with teens. Whether his anxiety comes from concern about a real physical cause, or the pain comes from anxiety, he needs to find ways to deal with the stress.
PM me if you ever want to talk.
If the chips are down, the buffalo is empty.