Seshi - good luck! That is great that you are going to try that - I used to really focus on what I hoped to achieve with the niggling/ being moody - I knew if I followed through the thoughts in my mind that I would not feel better at the end of it. It was a real effort - not easy I know - but I am so glad I did it and have stopped doing it now completely.
Of course, as Grace says, it only works if you are with someone who should be trusted - but even if you aren't - suspicious niggling will not control someone - ever. It's a big mistake that jealous people make, thinking that if they are constantly watching their partner they will actually stop them cheating. In the end - you have to sit back and trust - then have clear boundaries of what behaviour you will tolerate. ie. know that you would take action if something did happen. But - you can't be watching for it all the time.
MWJ - I have had all those symptoms you describe - it really is physical isn't it? I get my heart beating, total fear - I think there must be a physical pattern in our brains created by earlier events in our childhood.
It's interesting that you say the warning signs were obvious - I think the truth is - being jealous is unncessary - you can trust people and know that if something goes wrong that will be clear at the time. You cannot live on a constant state of suspicious alert - it actually doesn't help control people at all. Also, you didn't end it presumably? I think the insecurity and terror of being abandonded that all jealous people have - basically leads to clinging to shit situations.
IN fact - if you are always anxious I think you are less likely to know when to really end it.
I have always been absolutely terrified of being dumped/ left/ abandoned - to the extent that I would clinc to really awful men and hope desperately things would improve - this is a vicious circle because then you are confirming to yourself that all men really want to do is run away!
If you make a decision that you will only be with someone who really wants to be with you - then that won't happen.
I read somewhere that it's helpful to divorce your feelings from your actions too - ie. accept you have a jealous feeling but know you don't have to act in a jealous or suspicious way. Dont be hard on yourself for feeling like that - but do know that it's not useful behaviour.
My dad once said to me 'oh waterrat you cant expect men to be certain about you, they never are. ,just find one you are certain about and cling to him' !!! how sad is that - his advice to his own daughter, just reflecting his own issues. NO wonder I turned out nuts.
I am also a very cheerful confident person in other respects - friends at work were astonished when I told them of my mad thoughts - people think of jealousy as a weakness but actually it's just something that has been created in you by circumstance.
As Gandalfy mentions - I think the complex relationship between the person you are with and how you feel about yourself is important.
I am now with someone wonderful and calm and never jealous - who would never ever want me to be jealous and is completely secure. But I still have recurring dreams that he has left me/ that he is gone/ that he is dying in front of me. I feel embarrased admitting such madness!
IN the end, you have to 'decatastrophise (good word eh) your fear that your partner might leave you - accept people are fallible and you can't control the future - and know you will be okay whatever happens.