Can someone clear this up !

Okay, it's this big thing going on about who my child father is when I know for certain. But everyone keeps asking and now im even second guessing myself.  Here is the line up I last remember me having sex with my ex- boyfriend July 10th to be exact. it's a possibility the was another time around the 18th-20th which my boyfriend now claims he saw in my phone. I found out I was pregnant Nov 8th measuring about 6-8 weeks cant remember exactly. My last menstrual was sept 28th but people say you can get it and still be pregnant. Measuring from the first day of my last menstrual in sept not the date I may have conceived doc said im due late June. My period was a week to two weeks late in September but I did a test and doc did blood work it came back neg. She herself thought I was pregnant because my period still didn't come but it came down the following day. Still it should have showed up by then if it was my ex ? right ? btw my Last intercouse with my current boyfriend around that timing was October 2-4th. Which lines up with the timing of everything else. I went to the doc today and I am measuring 28 weeks and 1 day. I am safe to rule out my ex- boyfriend correct ?