My period didn’t show for December, and still waiting.

I’m 15 days late. I see a faint line, the thing is, I was pregnant before( January 2018, ended in MC) and never had to question the test, squint, or strain my eyes to see a definitive positive when I took one, why are the lines I’m getting now so faint? Or how long should I wait for a BFP? I feel like it’s not true.. :( I’m so confused.