Is it possible to ovulate without positive LH test?

Back again with more ovulation testing questions! (Sorry!) I'm now on CD 18, still no positive on the ovulation tests. I know a lot of women here say they didn't get one until CD 20-25 so I'm still a bit hopeful, but my doctor told me I have a 28 day cycle. Could it still be that late or was she maybe just incorrect about my cycle length?

What are the chances that I did ovulate and just didn't get a positive? This is my first month consistently testing like this so maybe I wasn't doing it right and I wasn't able to do it at the exact time every day but I've done twice a day since CD 7. One in the early afternoon one in the early evening and followed instructions on the test box. I also did have egcm when my app predicted me to ovulate. My app says I can take a pregnancy test in 6 days but is that true if I never got a positive ovulation test? We've bd every other day. Sorry, so many questions, I know. TTC is so confusing at times.