So confused

I had a really short cycle of 21 days last month. This month glow is telling me I'm due on day 24 which is tomorrow. I'm not sure when I ovulated as I never got a darker line on an opk. They were all just under. I felt like AF was coming on day 19 & a little bit on 20 but since then I haven't felt anything and I'm day 23 today. All I've had is back pain, mild nausea for the last 5 days, mouth ulcers and pelvic pain which I usually get around ovulation. I took a test this morning and it was BFN. anyone have any comfort in advice or am I out?