Latest you got your BFP

Mrs
Hi ladies! Looking for some advice here. DH and I have been TTC for 15 months, it's been a bumpy, emotional, roller coaster. 
My cycles are "normal" between 26-30 days, however I do have hypothyroid and am taking medication to regulate it. I ovulated this month around day 13 I think. 
Anyway, we took my mom out to dinner for her birthday last night- so I decided to test because I thought it would be a wonderful birthday gift to surprise her with as she has been super supportive with me and my hubby through all of this. It wasn't FMU, but by 12DPO I figured it should show up positive no matter what- if I am. Right? Anyway it was negative. And of course like every other month the wave of sadness begins. But I still haven't gotten any AF like cramps, indicating she is on her way. I did start doing acupuncture weekly to assist in fertility this month. So maybe that's helping my cramps? Trying not to think too much into it. 
My question is, with my cycle length is it possible to get a negative test at 12dpo and still be pregnant? Looking for some advice, sorry this ended up being longer than I thought. But I truly appreciate any advise, thoughts or kind words. Tomorrow is day 28, 14dpo and when ovia expects af to begin. By now I'm usually feeling cramps that she is on the way... 🙏🙏🙏 praying for our 🌈 ✨