Hi there,
Not sure about the fibroids, no experience with them.
But I had my 3rd baby in 2009 at the age of 41. (Had my first at 35, second at 36). We thought (well, DH did anyway) that we only wanted 2 for the longest time. Just after my 40th birthday we had 'the talk' and decided to try for #3. Month 1 I got pregnant and we now have the gorgeous and chubby Grady toddling around the house.
BTW, I was never a 'normal' weight for any of my pregnancies. Including my last baby, I was about 45-60 pounds overweight going into each of them. I had textbook pregnancies and normal deliveries - in fact Grady was born at home with a midwife and no pain medication.
Like others said, do what you feel in your heart.. don't wait for a number on the scale or worry so much about your age - or maybe it'll never happen. Sometimes you just have to take the leap and see what happens!
GL!