Its hard to say what that is from but it sounds like it can be an internal smooth muscle which is not able to maintain itself in proper position inside the body. This can be due to a spleen weakness, since spleen helps hold all muscles in their place. But its hard to say at this point.
Id like to have a detailed chat with you and see If I can help pinpoint the problem.
E mail me at firstname.lastname@example.org with your screename if you have one, and I will contact you.