Due date changes

Hey moms. Ftm and I'm wondering how many times your due date changed? Based on when I was ovulating and when my husband and I had sex I would have conceived the 1st or 2nd of February which goes along with my initial due date of October 24th. I then had an ultrasound in the er after unexpected bleeding on feb 19 and they said I was measuring 4w5d so the due date got bumped up. However at my follow up with my ob on March 3rd they said the baby was measuring at 5wks 6 days so they moved my due date again to October 28. The strange thing is none of these match when I believe we conceived. Just wondering if any of you ladies had multiple changes in how far along you are and if typically once baby is easier to measure if it's easier to get a more accurate timeline?