Since Mon 11th, Ive been suffering with constant feeling of nauseousness, bloated/tight tummy, light head and dizziness.

I originally thought it might be pregnancy symptoms, but a test on the 14th cam up BFN. AF was due on 19th, but on evening of 15th I started with light spotting which has gradually increased over the week.
It was all old dirty brown blood, and no bright red blood which I usually expect to see. My AF is normally 4 days, but this has lasted a week and is more of a discharge than blood.

I started with sharp pains to the left of my belly button, almost like a stitch, and although GP said tummy was nice and soft, I was tender in places and she too wanted a pregnancy test doing- results due back 26th.

I did another test myself yesterday which came back BFN as expected, but my pain started getting worse and I also had a hot tingling sensation either side of my eyes.
I went to the on-call doctor, and a sample I gave showed no water infection. He sent me home and told me to take paracetamol to see how I felt this morning. He said it was difficult to tell, but could be either concealed pregnancy, ovarian cyst or bowel problem.

I was sick this morning, but as my pain had eased, I felt it didnt warrant another trip to the hospital. I did have a sharp stabbing pain in my pelvic area that lasted no more than a couple of minutes. I feel so drained and exhausted though. Ive slept most of the afternoon, and less than a week ago I was beaming, full of energy, and now I cant be bothered with the simplest of tasks.
Im eating as normal, and going to the toilet as normal and drinking plenty of water.

Ive really rested up today but just feel so rotten. Tests are coming back negative, yet Ive felt like this for 10 days now and its not easing up.

Does anybody have any ideas please?
Thanks