Headache, Nausea/Diarrhoea, pins and needles.

Please help.
I am suffering horrendously with all the listed withdrawal effects after stopping Sertraline 3 weeks ago. :scared15:
I have just come out of hospital after a 3 day stop, during which I had a brain CT scan as the doctor in A and E thought I may have had a brain haemorrhage. Thankfully this turned out negative.
My GP came to see me today ( WOW a home visit!!! ) and she wants me to go back into hospital for a lumbar puncture.:ohmy:
I tried telling her that I had classic withdrawal symptoms after stopping Sertraline but she said that after 3 weeks I shouldnt be having any problems!
I cant eat anything or even drink water without feeling like I am going to be sick or running to the toilet.....lovely !!!!!
Will someone please tell me that these symptoms will go away.
How long will I feel like this?
I am so alone, as my husband says I am boring, and when my mum came to see me she stayed for about 2 minutes before saying that she had had enough of it and left. ( Does she think I enjoy feeling like this?????????)
How come nobody seems to understand? Why does a newly qualified GP not know about SSRI withdrawal?????
Will someone please help me as I seem to be feeling worse as each day passes. I keep having terrible nightmares too which leave me so worn out.
Jo x