how much should a mom's fertility be affected by her 14-month-old only nursing 2-3x/day (some days *only* at bedtime)?

almost 39-yr-old mom of 14-month-old (first child) has been trying to get pregnant for 6 months now and reproductive endrocrinologist told her that he won't see her again until she's completely weaned because nursing could be interfering with ovulation, and when mom requested blood draw for hormone levels, r.e. told her it just wouldn't be worth it.
first pregnancy was a loss at 12-week-gestation. "just couldn't pregnant" after that- successful conception after clomid & IUI. 
mom's first period was at 8.5months postpartum and she's had cycles ranging 24-33days since then (she knows it *could* be anovulatory bleeding, so she's going to start taking her basal body temp this month).  she's "torn" about weaning her toddler, who is obviously eating solids :-) and is sleeping all night. 
am I crazy to think bf isn't what's keeping her from getting pregnant?

help please :-) for specific information regarding hormone levels/fertility at this toddler's age and the (in-)frequency of bf. mom says she hates being in this situation, would love to continue nursing,  but hears her biological clock ticking and really wants to get pregnant again, would love to pick back up with toddler if she gets pregnant before completely weaning. mom is in philadelphia area.

thanks,
vicki hayes rn ibclc, mom of 3, brunswick ga usa

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