Mai,
I wouldn't assume that your doctor's advice is the last word on this. It's a very personal decision that you ultimately have to make yourself. Doctors are naturally going to favor a choice that protects your health, but this is an issue that affects your life as a whole, not just your health.
Yes, pregnancy has higher risks when you've had aplastic anemia, but there are also higher risks when you're older while carrying a child. There is no perfect solution.
You've gotten input from your doctor. I'd suggest learning what you can from a fertility specialist next, asking them to talk to your doctor directly to understand your situation. You can look through these forums for pregnancy discussions as well, and talk to the caring experts at the Aplastic Anemia & MDS International Foundation (see their
Patient Educator and
Peer Support pages). Then you can talk it over with your family.