I sure understand your problem and the embarressment.
Please be assured that this is not a rare thing and many people world over have this similar problem, just that they do not come out of the closet.
You have typical symptoms of O.D.S. (obstructive defecation syndrome). This means that the inner wall of your rectum
has become loose and is sliding down during every motions, so you get the initial motions but then the sliding rectal inner wall blocks the outlet. Because of the sagging wall, you still feel that there is something in the rectum that needs to come out, so after passing the finger, you are actually displacing the sagging rectal wall and allowing the stools which were trapped above to come out.
when you have a false feeling of crapping and nothing comes out, it is the sliding rectal wall which you are feeling and one equates it as stools in the rectum and thereby an urge to pass motions.
Also once labelled as IBS
, the tag goes on for life which needs to be re-confirmed.
I recommend you to undergo an MRI-defecography and Ano-Rectal Manometry at a tertiary G.I.Surgery / colorectal surgery
/ pelvic floor
department / proctologist
in your area.
Your problem can be cured by a surgery called STARR (stapled trans-anal resection rectopexy) if the MRI and the manometry reports indicate.
wish you good health