Here's the thing: It's not that unusual to be pregnant and never take a positive urine test. I never got a BFP by urine test with my DD. I thought that meant something was wrong with the pregnancy, so I called my Dr., who told me, "If it's positive, it's 100%. If it's negative, it's 50/50". Since it happened to me, I've met other people that happened to.
It's not that unusual to get pregnant while on the pill. At best, it's 99% effective, and hell, I know 100 women, don't you? 1 of them is gonna get pg on the pill. I did.
It's not that unusual to get pg on the pill and keep having "periods". If you don't know you're pg and take a test and get a negative, well, you keep taking the pill. When you take the blanks, you'll bleed, and think you're having a period. Thus, you have a period all nine months because of the pill and don't really think anything.
It's not that unusual to not feel baby kicking. Because of how some women carry, they just don't feel the kicks. I know at least two women planning to be pg, hoping for the kicks, getting prenatal treatment, reading all the books, etc., who just never really felt the kicks. Weird, but not that weird.
It's not that unusual to gain weight all over or not gain much weight at all while growing a perfectly healthy unborn baby. Some women distribute their weight differently. Others are already overweight so they actually lose a bit while pregnant and look thinner.
It's not all that unusual to be pregnant when you don't really want to be and stay in denial about it a bit too long hoping it's not really real and avoiding coping with the news. I know LOTS of people in that circumstance.
I guess what's weird is not that one of those things could happen to someone, but that ALL of those things could happen to the SAME person. It's a really unlikely convergence of events that must work out for a person to not know they're pregnant until they deliver. Maybe each of the events, by themselves, isn't all that remarkable, but all of them happening to the same person at once, those odds have to be out of the world!