Missed period

So I feel pretty sick right now (nauseous, headache, slight fever, aches, and dizziness) and have felt this on and off sickness for about 2 weeks now. Right now it is the worse it has ever been. I thought I might’ve been pregnant because I am today 9 days late but all 3 pregnancy tests that I have taken came up negative. I took one 6 days before my predicted period, one on the 1st day that my period should have started, and one test 2 days after that and they all came up negative. Me and my fiancé have been actively trying for 3 months now. What should I do? Thoughts?