to the original poster what you posted can be any number of physical or mental or normal problems...

examples of what this was/is in me...

multiple sclerosis
PTSD
Bipolar disorder
Anxiety
work stress
Anemia
eating disorder
sleep deprivation
dissociative problems
too much cafeine
too much sugar/ not enough sugar
too much salt/not enough salt

the list goes on of the many mental/physical and normal things these problems are in me

we can not tell you what this is with in you, to find out what the feelings are in you, contact your or a treatment provider (medical doctor, therapist, psychiatrist) they will be able to diagnose the problem in you.