Fertile looking CM but ovulation test said no..?

Samantha
Hi I'm fairly new to Glow & have so many questions!
My husband & I have been TTC for awhile now & we haven't had any luck. I've talked to my DR about it & after a round of tests she prescribed Metformin for me. 
Glow says I should be ovulating (Glow is usually spot on, give or take 1-2 days, about AF) & that I have a 33% chance of pregnancy today. However, my ovulation test was negative (The test line was there but was very faint & slightly lighter than the control line...). Does this mean I'm almost ovulating? Is a faint line better than no line at all? I'm so confused. 😔
Please help!