HPT can give a positive result 3-7 days after a missed period. Yo have tested early for the result to be obvious. Please wait for a few more days and repeat the test. If you wish for an earlier confirmation, please get the blood pregnancy
test done. This is more specific and sensitive as well. This would be better in your case as you have irregular periods
and the exact date of ovulation cannot be predicted. Your symptoms suggest very early pregnancy. Hope you find this information useful. Wish you good health.