I Got Blood Clots And Blood Tissues During Urination, Did I Have A Miscarriage ?

so a week ago everytime i pee i would bleed but i will also pee blood tissues and ablod clots and i was not on period it also hurt it. now i went to the clinic they did a pregnancy test and it come out negative about an hour after i got home the clinic called saying it came out positive that i might of been having a misscarriage. but i bought a pregnancy test and it still comes out positive.i went to the clinice to know how far along i am for the ultra sound but they could see anything with the ultrasound or vaginalsound? am i still pregnant or did i had an instant misscarriage? also since my actual period should around this day i get mild cramps? whats going on?