Hi,
Menstrual cycles with a length of 21 to 35 days can be considered as normal. According to your history you had around 20 days menstrual cycle. We can consider it more or less normal only. If the menstrual cycle length further decreases in next cycles, you may need to get evaluated.
Now, as four urine
pregnancy test kits gave negative results, the possibility of pregnancy is less. If you want to be sure, please go for
blood test for pregnancy, which can give a more accurate result.
Beta HCG values of less than 5 mU/mL, will rule out the possibility of pregnancy.
Regarding your symptoms, Gastrointestinal causes, especially severe
gastritis can also present with these type of symptoms. So, better to consult a Physician once and get evaluated. Clinical examination and if needed
endoscopy can help in finding the possible cause of the problem and treatment can be taken accordingly.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Sree Gouri S. R., OBGYN