Can anyone tell me whats wrong with me?

Here it is, my head has not been 100% for a few weeks but it has got better, i immediatley thought that i had a fatal illness and now i just can not stop worrying about it apart frop when im doing something active or when im focussed on something, however when im alone i start to worry about it again and im sick of it does anybody know what it is....I also have blurred vision on occasions when i look at far away things. i went to the opticians and she said my eyes were perfect and that there was nothing sinister in my head. please somebody help!