Pregnant and how far?

So found out today I'm expecting... Mixed feelings completely and that's a story for a different day. Anyways, I'm not positive on how far I am though. My last manstraul (if you want to call it that) was in April, but was for like a day and a half, and spotty. So, do I consider myself 4weeks 5days, or 8weeks and 5days? I do have a 3yr old and she was a very hard complicated pregnancy and was on bed rest at 14 weeks and I'm worried of this is going to be the same. Advise......