Dear oh dear, you really do need to get a grip of yourself.
You do not have a brain tumour, the MRI scan would've picked this up if you did, so relax and rejoice that you are not cursed with this horror condition.
The diagnosis of your condition is obvious, you are completely neurotic. You have high blood pressure, palpatations (hence the chest pain) and all the other symptoms caused by stress.
You need to get out of the cycle you are trapped in of fearing you have a severe illness, this may require medication, possibly anti-depressents. I would then strongly suggest taking up sport, even if its going for a walk. Get out and enjoy the world and stop worrying about things you have no control over.
The alternative is to remain trapped in your cycle of paranoia, which will just lead you to higher blood pressure and probably premature death.....not from a brain tumour, but a heart attack caused by stress.