I presume you haven't had a period after 13 April. The info from your question are barely adequate to give any reasonable opinion. Were your periods normal till March? Do you have your thyroid
status checked? Did you take any medications like emergency pill or any other hormonal
medicines? If its already 1 week passed after your last negative test result, I suggest you repeat it. A thyroid function test and an ultrasound
examination of your uterus
and ovaries will help to reach a conclusion. Please consult your doctor.