I have read your question,
The symptoms you stated could due to Pseudo pregnancy
,In which women think that they are pregnant and also feel nausea
, high urine frequency , vomiting
,giddiness,a feeling of movement in their lower abdomen, loss of appetite , but this is just psychological .
I have seen such cases before hence I Am concluding so . Moreover Your tests were negative and since you have regular periods , that concludes that you are not pregnant .
For your satisfaction I recommend you to undergo scanning examination of pelvis By a certified gynecologist nearby.
Wishing you a good health,