Dollar Store Ovulation Tests

Sheena • 38yrs old, wife, social worker, beautiful 6yr old 👦 via IUI in 2015, TTC #2 since January 2018. Stage 2 Endo. 👼 👼 🌈
Due to financial circumstances I have been using Dollar Store ovulation tests. Friends who successfully conceived have used them, but in 3 months TTC I have only seen 1 positive ovulation result. 
​Any opinions? Do you think it makes a difference to purchase expensive ones vs. cheap ones? Obviously it's possible I just am not ovulating.
​GLOW app is telling me I am ovulating now ... Tests say otherwise.