Help pls :( ovulation and u.s

I took ovulation test on day 9, negative day 10. In the morning almost positive i took a test again in evening its postive i took again on day 11 and its surely positive i had an u.s today and my dr. Said that theres no ovulation happen 😔😔😔.. I take 7.5mg of letrozole day 2-6 of my cycle.. Is technician did not see any follicles or something that confirmed ovulation, is there any chance that an ultrasound be wrong , should i rely on BBT and OPK or the ultrasound, its been really long since we started TTC 😢😢