What’s going on? Any similar experiences or advice?

We aren’t TTC. My 18 month old is still breastfed. I only mark “♥️” on the days that we DO NOT use protection. Promise our life in the bedroom is more lively than this chart lol. But I didn’t have a period at ALL for July. That’s not normal for me. I took over 20 tests (seriously went through a 20pk of test strips + other brands..) and no positive. I don’t think I’m pregnant but where’s Aunt Flo??