I might have had the same condition or certainly same symptoms .
Mine was stress related and being stressed out causes your sphincter to push out where as it should constrict in.
There are a few easy ways to check if it's stress.
First are you tensing pushing out your stomach muscles. Check them you may not be aware you are (I was for years and not aware I was doing it)
Your stomach muscles should be relaxed .
If you are pushing your stomach muscles out you are also pushing your sphincter out.
Try doing this in the shower
Touch your finger on your anus opening , pull your stomach in and take a deep breath at the same time. You should feel your sphincter contract in naturally by reflex.
To fix it can be easy and not so easy. Bear with me
First of all
STOP forcing your stomach out.
Hold it in when ever you think of it . This may take a while but eventually you will do this with out thinking and by reflex and after a while you will notice when your stomach is forcing out because it feels unnatural (another Benefit by holding your stomach in you will find you become less constipated and more regular)
Second of all
Take DEEP breaths whenever you can .Taking deep breaths will naturally constrict your Sphinter to its correct position and make it stronger with each deep breath
It's as easy as that!
Now the not so easy bits
You have deal with and overcome what has stressed you out in the first place .
Hopefully your major stress now is your odour problem and you have forgotten what caused your stress in the first place. If this is the case then your cure could be easier than you think.
Hold your stomach in and take deep breaths.
If you have forced your stomach out over a long period it will probably take you a while to get out of this habit completely and initially you will find
Yourself slipping back to bad habits don't give up
Just take Deep breaths and hold your stomach IN when ever you think of it .
Exercise is good for stress .
If you have been forcing your Sphinter out for a long period it might be worth strengthing your muscles by constricting it intentionally for a few minutes every hour for a few weeks but remember by taking Deep breaths you will be doing this
anyway just not as intense.
Also when taking deep breaths make sure you exhale by relaxing NOT forcing . If you force your exhale you run the risk of training your body to force your stomach out again
Anyway I hope my problem and solution can help some people here . I was really sad to hear the loneliness and despair of some you.