What Causes The UPT To Be Positive And Negative After Missed Period?

i am 37 yrs old never been pregnant. on the 4 day of missed period i took home preg test came out positive after that i experiencing early pregnancy symptoms. after 8 days since i missed period i started having some spotting. on the 2nd day i am having a light bleeding i took another home pregnancy test came out positive later that day bleeding became heavier and i notice my breast arent sore anymore and some symptoms are also gone.. i went to the hospittal they tested me i came out negative i wonder what happen pls explain to me what happen there. thanks