Long rant. Beware!

Emma • TTC lil babe #1.
At 10dpo I had a very faint line on a frer, a negative that night, another faint line the next day, a negative this morning at 13 dpo (I think I flooded the test with too much urine) and a very very VERY faint line this afternoon. I'm wondering if it was light because my urine was dilluted. 
Questions!!
1, has this happened to anyone before?
2, has anyone only tested pos in the afternoon but not with fmu?
3, is it strange the line isn't getting darker? 
All were taken on frer. AF is to arrive tomorrow/Saturday ish. 
Update: wouldn't it be very rare to have three false positives?