What is this?

AF was due yesterday. Iv been having pink and brown spotting and on and off bad cramps. Small stringy clots too when I pee. I tested yday and got a blatant negative. Today, still not enough light blood to fill a pad. Then I got a very faint positive pregnancy test and this (TMI) when I peed to take the test. What does that mean? (It's a small cup) has anyone else experienced this? Xx