My doctor says I am six weeks pregnant. I know when I conceived and think I am 7 1/2 weeks pregnant. Can this be correct?

If you can tell me the first day of your last period I can tell you when you conceived and how far along you are.

I wasn't getting my period because I was underweight. I gained weight but before I started getting my period my doctor induced ovulation with Puregon and Repronex. Then when my follicles were mature, I had an injection of FSH. I think I conceived around Sept 11th-12th.

There is no real way to tell the difference of one week conception. You would know the dates you had sex. I guess is there a real issue if you are 6 weeks or 7 weeks?

One to one and a half weeks makes no difference whatsoever. Go by the due date your doctor has given you. Pregnancy is all a guessing game. When it comes down to it, we in the medical profession, look at your due date either 2 weeks before or 2 weeks after what the doctor has told you.