Still getting negative ovulation tests?

Hi everyone,
My partner and I are trying to conceive and I'm using ovulation tests for the first time since my cycles aren't regular.
I've been testing for 5 days in a row now, starting from day 10 of my cycle, but every time it's negative. For the last 2 days, the line has even been lighter than on the first 3 days.
I'm also checking my discharge, which has been creamy white until now, but since today it's a bit stretchy and egg-white-like. Normally, that means I'm fertile or becoming fertile, right?
But why are the tests always negative? Because of this, I'm not sure when exactly my ovulation is happening...
Can you help me??