OPK question

Kelli • 31- Married 💗 - Momma to a sweet girl 💕 Expecting Baby #2 in January 💜

So, I've been doing OPKs 2x day for the last week. I kept getting very faint lines, but nothing solid,they were all hard to see. Glow now says I'm in my fertile window (third day in) and my opk was 100% negative. Not even the faintest hint of an LH surge. Is it normal to get faint lines then nothing?