Val,
I will start my response by saying no one here, for certain knows exactly what this entity acually is. It may be true shadow people, a demon, a non-human entity, a really nasty human spirit who can make you see it in any form or any number of different types of negitive entites.
The truth is we dont know.....
It is in my opinion that you will not be able to send this thing on its way without the help of a very experienced individual....like a medium, clergy, shaman, reki master ect.....possibly a combonation of gifted people.
If the entity is truely a shadow person they are very hard to get rid of and I dont think you should be attempting to get rid of it on your own. You have already done what you could with the sage, prayers and stones. Im sure there are other steps you can take but I caution against it.
Cleansing can work for more powerful entities however there are situations where the cleansings helps for a short time but then the eneity is back....and usually more aggressive because it knows you are trying to get rid of it.
It is not my intention to scare you but I FEEL you need to ask for help ASAP!!!!!! I can't say it loud enough (literally, I am yelling at my computer) or too many times......GET HELP!
This is nothing to mess around with and considering that you have had paranormal issues your whole life, it is possible that the entity (s) has been attached to you for some time.
FYI...A gifted person who doesnt acknowledge their gift can end up with plethera of issues. Im not saying you have to use your gift, I am only saying to try to understand it. It may shed some light on why you have had experieces all your life.
Light & Love