My skin has lost the ability to stretch

My skin has lost the ability to stretch. It's not all stretched out and floppy, it just won't stretch any more. I'm 65, and I'm not worried about looks or anything like that. It's other problems. I can hardly get my mouth open wide enough to get my partial plate in. Other areas on my body the skin has become so tight movement is difficult. Nothing looks odd or different. I have no strange illnesses I know of. High blood pressure, Cholesterol, but they are under control. The only odd thing I know of is I don't have a Pituitary Gland. Lost that in Vietnam but I take artificial growth hormone to take care of that. I was wounded several times but I've been okay up till now. I'm not overweight and in good shape muscle wise. This is affecting over half my body and it's really starting to bother me.  Anyone have any ideas? I'm being shuffled off by the doctors with an "It's all in my mind" routine. It's even affecting my sex life and that gone far enough!

Frogman.