Disappearing Line or Evap?

Today I'm 12 dpo. I had a missed miscarriage in Jan and had a d&c. DH and I just started ttc again. Yesterday I took a First Response and thought I saw a very very faint pink line before the time limit was up. The line was a little darker on the bottom half, but was still very light. That line has stayed the same in appearance since yesterday. Today I took another First Response and again got a very very faint line that looked pink. After a few minutes of looking and looking again, the line seemed to disappear. After the time limit, it looked like it reappeared but couldn't tell if it was pink or if there was any color. I'm guessing the second test was an Evap line but is it common to get a faint positive and then get an evap line the next day with the same type of test? Or does it sound like this is just a BFN?