Evaporate

So this morning's test is basically bfn.  I waited for 30 minutes trying to see something but didn't.  Then when I got up 2 hours later there was a clear evaporate line.  Gray, thin and very faint, but visible and maybe a shade more prominant than the evaporate 2 days ago.  Yesterday's test is still stalk white.
So I am left with a few conclusions.

1. That I have hcg in my body but the levels are so low that it takes hours to show even a faint line and since the line is so thin and faint it has no color. 
2. That it is a true bfn being gray and way after the time limit.  The only reason why I have a hard time believing this is that my test yesterday showed no evaporate line and same with all the tests I took ttc #1.
3. The dollar tree tests are just not working with me this time.  For my past pregnancies I got clear bfp by this date, but I had high beta numbers too so maybe that is why. 
Pregnancy #1 I got a visible bfp at 12 dpo (didn't test on $tree tests before this) and had a beta over 100 at 14 dpo.
Pregnancy #2 I got bfp at 10 dpo (didn't test earlier) and at 14dpo my number was over 250.
So doing the math I had a beta around 50 when I first tested.  The $tree say they pick up 25 or above.
I'm just guessing that if one embryo did stick that it was late and the hcg is very very low.
I don't know.  Will be buying some frer this afternoon.  Looks like I have no choice but to test again.
I really hate wasting the money on the frer without a clear bfp on the $tree tests, but I can't stand this maybe, maybe not answer, though I must say an evaporate is still better than yesterday's stalk white result.  Even if the evaporate is false at least it is giving me a bit of hope today.