Pull out method on fertile days
If I understand it correctly, the My Days app uses only a calendar method of determining your fertile times, and if you've heard any jokes about the rhythm method, you'll know that it's not as effective as many other forms of birth control. Additionally, the pull-out method is not the most reliable. There's a lot more research on fertility that can be used that would give you a better idea of when your body is preparing to ovulate and when you have actually ovulated. Check out the charting to avoid thread for more information on that.
If you did actually ovulate when the app thinks you did and you were actually 10 DPO when you did the blood test, it is very unlikely that you are pregnant. Usually, implantation occurs on or before 10 DPO, and there would be at least a little bit of HCG by then to detect. However, I don't have a lot of trust in the app that it accurately determined your fertile days, so you can't really know for sure until your period starts or you get a positive test.
I think that a blood test would usually be accurate by 10dpo.. On a side not, though, my husband and I used the pull'n'pray method and our baby is now 8 weeks old. The method does work most of the time but it only takes one sperm to make a baby ;) I'd suggest something else if you're absolutely not wanting to get pregnant.
I would test again in a week. Pulling out actually has a good success rate when used correctly. 4% risk of pregnancy per year which is pretty good compared with other methods. "Typical usage" (ie. user error I'm thinking) makes it aoubt a 25% risk/year. DH and I used it for 3.5 years successfully and then conceived this baby on the very first try so I am a pretty big fan of it but would maybe not be if we hadn't been open to more kids.
We've used it for 2+ years with no problems. My general understanding is that as long as he hasn't ejaculated in the last 6 hours (in which case sperm could be released early) and if his timing is good, the odds are virtually zero. But like with any other form of BC, you have to be good at it and use it every time :)
Could you talk a little more about your experience with the "pull out" method? I'm in the same boat as the OP, 10 days PO, pulled out on a fertile day... the difference is, I do chart and I know I was fertile, and we had three pull outs in as many hours. I guess ignorant me, thought that sperm needs a warm wet environment to survive and re-entry after about an hour would be like starting over. My experience with family planning is we use a barrier method on fertile days, but since dd1 ( a planned pregnancy), my diaphram no longer fits and frankly, I have been single for 4 years so I haven't given it much thought! So, I'm waiting... and like OP, a baby would be a blessing too, but I just need to know. where did you find your "six hour" information? I would like to torture, I mean educate myself further :)
It's been awhile so I honestly don't remember but I saw something on another thread the other day that urination in between can be enough to clean out leftover sperm who might be hanging out. This link doesn't list a time but does talk about urination: http://www.plannedparenthood.org/health-topics/birth-control/withdrawal-pull-out-method-4218.htm
Regardless though on a practical level, your odds are probably extremely low. So if a few sperm make it through instead of the normal quantity that translates to very low odds any of them will make it to the egg alive. Possible but not likely.