headaches, nausea, fatigue and muscle aches! what could this be?

Hi all I need a bit of advice. I started to feel ill on christmas morning. I had terrible nausea and felt like i could throw up at any minute. I had no appetite and couldn't eat anything as it made the nausea worse. I also had a high fever and stomach cramp, i thought it was a stomach bug but without the vomiting.

On Boxing day i felt much better, a little tired but had an appetite again and the nausea was gone. I felt fine until wednesday 28th when the nausea and fever returned. I have been off work sick from Wednesday and since then have been exhausted. I have fallen asleep during the day several times which is not like me, I have had terrible headaches and every muscle in my body hurts. I was wondering is there some sort of virus going about causing these symptoms? A family member has felt the same. This has been going on for almost a week!