Brown small clot spotting

Today when I wiped I had a brown small clot there was no blood or pink in it. I tested positive on Thursday. And I was afraid I was miscarriaing. Has anyone experienced this? I went to the dr and they did urine test which they said was very faint they still said I was pregnant. But I think my lines are getting darker? I'm just so scared and worried anyone else had the same problem ?