Due Date Calculation

This may or may not be a concern to others but I'd like a better idea. I have the dates of my last menstrual cycle (3/30/17) & the dates of intercourse (4/8/17, 4/10/17 4/14/17) at which one baby was conceived. My 1st sono I was predicted to be 7wks. My 2nd sono I was predicted to be 13wks but baby measured 14wks. My doc is saying that my due date is 1/22/18 and will not change the date based on any sono's since the 1st one. I've researched all sites out there with pregnancy due dates and none of them predict 1/22/18. I do think I'm farther along. Shouldn't my doc consider the concrete dates I've given instead of the 1st sono? If anyone has any knowledge on calculating I'd appreciate it!