Xyphoid process. I sit ground level?

I have started feeling my xyphoid process since more than year now.. I am feeling it when touched.. that part does not have any pain ... I am diabetic since year now .. i have only problem is when I sit at ground , I feel stomach tight.. I never experienced this earlier .. I have been watching xyphoid process since year .. it is same feel and doesn't have any sort of pain .. I also consulted gastrologist and done Upper GI endoscopy .. nothing wrong in there .. that doctor told it is common and you are thinking too much ... I am not thinking too much .. I have just 2 concern 1. Why I started feeling my xyphoid?? When I take entire my stomach inside I feel it and I see it. 2. Why I feel tight /discomfort in stomach when I sit ground level ???