Dark brown blood ah!!

Caitlin
I am 14 weeks along and this morning I woke up and peed only to look down and see dark brown blood all in it :( I freaked out thinking miscarriage! Luckily my 14 week appointment was today. They were a tiny bit concerned at first but she checked and said everything looks ok and it might just be old blood because of my cervix expanding? She wants to see me again in 2 weeks just to check again. I feel better but still a tad concerned! Anyone else have this happened or know anything about it? Btw my baby's heartbeat was just fine they said.