I used metformin to conceive DS, and like you fell really quickly once a cycle was established. My cycle returned at 3 months after DS was born (even tho we fed round the clock for many many months!) and it was like clockwork (never had clockwork cycles before). We started trying for DD and fell 2nd try.

My cycle returned 5 months after DD was born, and again was clockwork.. until she was about 18 months old and my cycles started getting erratic again. We've been trying for #3 since June last year with no luck. I don't want to use metformin again, so have been using chinese medicine to regulate my cycles instead (have had beautiful cycles on this). We did fall pg last month, but it didn't work out.

Sorry... probably none of that really helps or means anything.. but that's my experience. Pregnancy & breastfeeding were my friends when it came to normal, regular cycles. But yeah.. it's all been going backwards again this last year and have needed help with my cycles.