Positive now negative ?!

Hi everyone, so yesterday I just thought I’d take a clear blue test and showed I’m pregnant 1-2 weeks. Now this morning I took again just to see if it’s real or not, now it shows negative. This was a clear blue digital test. I took the pink dyes as well but all show negative.

Should I go for a blood test?

Last night I was so nauseous, tummy terribly painful and bad tummy upset. Feeling dizzy and bad headache.

Please help with some advice. This is my first time so it’s a bit scary