After more than a year I guess I'd post an update.
Blood and heart tests (ECG and echo) showed there is nothing wrong with my heart.
After the physical route started running out of obvious (and dangerous) options my primary care doctor referred me to a psychologist. She made me keep track of what I was doing each day and what caused me to be more fatigued.
Although I didn't really need a psychologist to do this, it actually helped me identify a few things I was doing which increased my fatigue.
Currently my fatigue is much less worse, and sometimes I don't even notice I have it. I am able to tolerate coffee and work to a much greater extent. Also my grades improved substantially (from trouble finishing courses to 8/10's) and at some moment I started to pass all my courses
These were the things which helped me greatly:
-Start exercising at a much more intense level (I used to cycle a few kilometers each day, but now I am also taking martial art classes which are fun and help a lot)
-Cut back on coffee
-Absolutely do not drink coffee after dinner
-Take these sleeping pills which contain melatonin
The exercising made me have much less heart palpitations and sweating. I concluded these 'spells' are some sort of panic attacks, because I can now sense when they are going to start (sweaty palms and a surge of 'fear' through my body) and I can calm myself down a bit.
The melatonin pills helped me to sleep much deeper, I'd feel much more rested each morning. The pills now kind of started to lose their potential, and I am now sleeping without them (the pills only contained melatonin and valerian, so I guess no addictive substances in there).