If you had your menses last week and full 4 days then unlikely that you are pregnant as you would have missed your menses completely in that case. The symptoms are more gastrointestinal rather than menstruation or cycle related.
You may increase your citrus fruits intake to allow taste to improve and keep yourself well hydrated. If the anxiety in your mind still exists pertain to pregnancy, then get a urine pregnancy test to rule out pregnancy.
I hope I have answered your query,
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