Don't often come to this section as not trying for a baby, but had a strange experience recently that I thought someone here might be able to shed some light on.
I'm on a break from the pill, DH and I not having much activity at the moment and have PCOS so no regular cycles. Anyway, 2 weeks ago we had our first and only activity in about 2 months, got a bit carried away, used withdrawal "method", I wasn't 100% sure it had worked, thought about but didn't take the MAP and then exactly 6 days later experienced a night of rather odd tummy movement.
I was worried enough about it to buy some cheap 2 for 1 Superdrug tests when I was out shopping the next day. Took a test, negative after 3 minutes, then looked at it 10 minutes later and there was a thin but distinct and easily visible pink line.
I took another 3 tests over the next 2 days (exactly 7-9 days after fertilisation, so baby officially 3 weeks old) and they all came up with a thin pink line although progressively getting weaker. I also took a Clearblue digital test at this time which came up "not pregnant".
I still have all the "positive" tests which still show the pink lines. It turns out the Superdrug tests are at 10ml HCG, whereas the more expensive Clearblue tests at 25ml. The Superdrug tests are today coming up completely negative, which for me is good news as a baby wouldn't be a good thing for us at the moment (sorry if this is insensitive for people trying here).
Anyway I researched like mad on the Internet whilst all this was going on, and the only thing I can think of is that it was a chemical pregnancy- which is something I had never heard of before but I know from posts here is quite common. I did learn a few things along the way which is that implanatation can occur as early as four days after fertilisation (rather than the 6/7 days usually quoted) and that cheap tests can be more sensitive than the brand leaders, although maybe not a good thing in view of the frequency of cps.