I have a very happy life, and was far from a career driven person, but if you want children- start soon!
If I had pushed for fertility testing and treatment earlier, I 'might' have been able to have children. 12yrs TTC, 3 losses, 2 rounds IVF and no fertility issues found in the end! I was fobbed off multiple times and 1 GP said I just needed to 'relax, and it will happen'! It never did!