I can tell by reading your posts that you really want this BF relationship to continue. I'm sorry that you are feeling down about things. You have been doing a marvelous job holding it all together!
I was wondering a couple of things. First, you wrote about dd's drop in percentile for weight. Could you give us her weight checks since birth (starting with birth, including lowest, and any up until now) and also her growth in height?
I understand that your physician was considering FTT as a diagnosis. Do you know what other symptoms dd had that would make them even consider this diagnosis? According to the BAB 3rd Revised Edition, Failure-to-Thrive in a baby older than one month is characterized by:
*weight below 3rd percentile
*drop in rate of growth of length and head circumference
*infant falls two standard deviations on the growth chart
*evidence of malnutrition, dehydration-sunken fontanel, grayish pallor, lethargy, loss of fat layer under skin, strong urine, inadequate stools
*infant does not meet developmental milestones
*mother experiences few let-downs
*erratic of nonexistant weight gain
I would suspect that the formula supplements did not help your supply too much. But, if there was truly a medical need to supplement and you could not do so with EBM, then the formula was important and it is certainly not the end of your BF relationship! (If it helps you feel better, she is older, and since she is eating solids, her gut flora has already been altered, so you can just look at the formula as another solid food she is eating that is not mom's milk! )
About fertility and your period: there is a very wide range of normal for when women experience the return of their periods. So don't feel that you are "out there" for having it return now. That is completely normal. Some moms go longer without a period, some not so long.
No, a body does not just stop making milk for no reason, so don't worry!
I am anxious to read your responses...hang in there!