What Causes Tiredness With Numbing Feeling In The Head And Chest Pain?

I feel sick at some point during the day, i constanly have a weird feeling in my head, its not pain as such, but like a numbing feeling and irritation. I feel like im going to phaint all the time, im weak and very tired, i also get chest pains from time to time & my breathing is rubbish, its hard to breath at times. I have had countless blood tests and all of them showed nothing! Whats can be? Thank you.