What Causes Fatigue, Muscle Weakness And Intense Pressure In Head?

I have been experiencing extreme fatigue, muscle weakness including muscle spasms, am very disoriented, can t walk for long without feeling like I m going to collapse, intense pressure in my head, running ants feeling in my fingers with occasional numbness (though I never change colour), am sometimes feverish too, and it feels as though I haven t slept in days though I have been have 8 hours of sleep each night. This has been on going for about ten days. I have seen my local gp, had tests for glandular fever and magnesium deficiency though they came back negative. I have never had issues with anxiety, and being only 20 I cannot attend my uni lectures feeling this way. Any ideas as to what it could be? Thanks.