Happened to us on our honeymoon! It was a rookie mistake on my part for not putting my pill in my carry on, but long story short our bags got lost in transit and did a nice little tour of north america for 2 days thus 2 days of no pill, also apparently mid-cycle. We're expecting our twins anytime from mid this month.

But tbh we'd been playing it pretty fast and loose, and I forgot to take my pill on the way over crossing the dateline and stuff (we went to the US). I think you have to be pretty lucky (or unlucky) to nab a sticky one off one or two missed pills, and it probably also depends on your natural fertility as a couple. Mum said her side of the family are pretty fertile turtles, and DH's family are the same, so its no wonder it happened to us - its more of a wonder it didn't happen sooner really!

You've already mentioned the endometriosis issue, and a family history of difficulty TTC, so you're probably right, you're probably not pg, but stranger things have happened and nature works in mysterious ways, so keep an eye on things because you just never know!