Can anyone help me understand ?

I get pregnant so easy I’ve gotten pregnant 4 times in the last 3 months, I take a test it comes back pregnant, I got to the hospital for blood work and tests my hcg levels were 17 and dropped to 1 in 3 days, and this happenes every time I get pregnant I’ve gotten tests done my ovaries and uterus and cervix are all normal it just doesn’t make sense why it won’t stick, someone please help me