Feeling sick and tired

I often feel sick and tired without any reason. My GP after running the tests says that I am fine. But I am still worried that something is wrong with me. I believe that a healthy person should feel good all the time and wake up being full of energy. There is no reason for me to feel sick and tired.
There is lots of thoughts and emotions about this:
Fear – what if I have an illness not detected by general blood test;
Frustration – my body is sabotaging my progress;
Compassion – it’s ok not to be ok sometimes;
Suspicion – what if I lie to myself that I feel sick as a form of buffering.
Curiosity – Maybe I have food intolerance or something else that could affect the way my body is feeling.
I go round and round thinking these thoughts and end up getting a headache making things worse.
I stay in bed beating myself up for not being productive and being angry with our health system that doesn’t do much to help me.