WHen did I concieve I'm confused?

Ok so I can't remember when my last period was, I know it was a Wednesday but can't remember which? I didn't have a period the week of the 10th November as I was out on the 13th and no period so it must have been before that, I had on the 12tg, 14th and 20th, I found out on the 28th I was pregnant, I started 'feeling' a bit pregnant around tge 24th, smelling more than usual, and a bit nauseas? So when was I likely to of concieved? Thanks :-)