You must be nervous! I would be, too. I rememeber worrying about taking anything in the frist trimester. However, since you asked your OB and you were told it was OK, then staying the course might be the best bet. Withdrawal, I am thinking, especially cold turkey, maybe have a negative effect on you and your baby.
Adderall is FDA pregnancy category C. It is not known whether Adderall will harm an unborn baby. Basically, no studies have been done/published on the effects of Adderall on a pregnancy or baby while in utero.
If you still feel unease about it I would call your OB again and maybe speak to a nurse who might offer up more information that might ease your mind.
You are the mommy and you need to do what is best for your baby and you.
usually they would use your LMP as a way to date your pregnancy... I wouldnt say the bleed you describe was a period, could have been spotting or implation bleeding...so going by your LMP I would say you are round about 7 and a bit weeks pregnant. The doctor though will do a scan etc and that will be a better way to predict the date :) Hope you have a healthy nad happy pregnancy.