Not ovulating?

Monica • 36 yo, mother of 2
I've got back my menstruation after the first baby in Oct (baby was 6 months) and we decided to go straight away for a 2nd baby. Now, there's no real rush, but I've been taking every day ovulation tests (even twice a day sometimes, different brands) and it looks as if Im not ovulating at all, not even a faint line there. The Glow calculated fertile window is closing today, we did have intercourse, but the ovulation tests were all negative. I'll keep testing, but is this possible? Anyone had the same? The menstruation looked normal, very heavy flow even. Baby is almost 9m old and still partially breastfeeding, but if menses are there I assumed I'm fertile again? Please anyone?