A friend of mine with PCOS found out at 26weeks. She had been taking hpt and they were all negative. Placenta was anterior too (on front wall) only found out when she did because she went to drs and was sent for scan. She and her DH though they would find a 8-12week bub, 26+ weeks instead!

With mine I have always known before 5-6weeks. But I didn't show or have many movements before 26 weeks so I can understand how others might not know. (size 12-14 here and have been since teens)