Re: running vs getting pregnant?
I got pregnant while marathon training, with a 39 day cycle, at age 36, and ran through week 40. So, as others have said, it can be done. (I didn't go through with the marathon, but did keep up weekly mileage of about 30 miles until week 30, then switching to indoor running and dropping down to about 20 mpw.)
Personally, I didn't bother talking to a doctor when I was thinking about getting pregnant b/c I was charting and had a very good grasp on what was going on with my cycle. Even if you do talk to a doctor, I'd recommend starting charting now, so you have actual information about your cycle when you go.
And an absolutely fabulous book about running and pregnancy is James Clapp, Exercising During Your Pregnancy. I think it's the best book on this subject out there - it gave me the information I needed to keep running until the end! (Now, getting a baby and myself out the door on time for a run before work is a whole 'nother story...)