Why Am I Having Pregnancy Symptoms In Spite Of Having Period?

Hi am 25yrs old,and i have problem about pregnancy,we had sex last month and again i had my mense 12 of this month,but i have all the sign n symptom of pregnancy,my breast engorse and produce milk which taste sweet, i did the test but its negative,i don't want to get pregnant now, please help me,my age 25yrs,height 5ft2inch,weight 42kg