POAS addict and very faint lines!

Anna • Married since 09/09. We have a beautiful son, born on 2/11/13 at 36 wks 3 days. Ttc#2 since June 2014. CP 10/19/14 :`(.
I am 12/13 dpo and have faint (very faint lines) and AF was expected yesterday. The faint lines were visible on FRER with FMU and I took a CB digi to just confirm. But I got a BFN and tested with a faint line apparent on the wal mart cheapie. What in the what! I am also experiencing lower back pain, fatigue (I do have a 20 month old-I acutally always tired), no soreness, even had pink cm yesterday. Ahhhh. My first pregnancy was pretty straight forward and I got a very obvious positive on 12dpo. -Still hopeful.