What could possibily cause all those symptoms?

I wonder if anyone can help me. I have been going through
strange periods in my life, starting five years ago. Out
of a sudden, my life turned from calm and steady to crazy
like a rollercoaster. I have heard about similar events
when people brain mature around 25-26 years old
but there were certain symptoms has arised out of nowhere
and almost sudden as follow:
1) I felt that I will die soon and was somehow careless
about it. (I no longer feel this way)
2) I saw white hair, show in my scalp and front hair,
not alot but visible.
3) I stared to gain weight alot, although I was always
average weight, lean toward being slim.
4) I was very emotional, and cry alot with or without
a reason.
5) My average heart rate was high, had exercise intolerance,
chest pain, dizziness, almost faint experience.
6) I became sick more often almost three or four times per
year, hardly recover from illness.
My doctor says that I am healthy, all my blood work came back normal
What could possibily cause all those symptoms? Tweet