Quoting Jamie & Baby Aria (::" Yesterday my OB prescribed birth control for me, but I haven't been able to get it yet, and since I'm ... [snip!] ... so I'm hoping she prescribed something that won't ruin my supply; I've worked really hard to be successful at breastfeedin
First off sorry for a long reply. And please don't worry about your milk supply. Let's discuss your first questions about being pregnant. Well, have you ever heard of lactation induced ammenorhea? If you are exclusively breastfeeding I mean no pacifiers, or supplementation of expressed breast milk there is a small likelihood that you will NOT get pregnant only 5 weeks post-partum. lactation induced ammenorhea is over 90% effective within the first 6 months after delivery. That mean no period for mother's who are EBF and not giving artificial nipples to there baby and feeding on demand.
Also the mini pill is a progetserone only pill and it can effect your milk supply if you are having issues with supply already. Progesterone has the ability to suppress the efficacy of Prolactin levels. (prolactin is the hormone responsible for milk-production.)
But I REALLY wouldn't worry about it effecting your supply if you have been breastfeeding well, because by 5 weeks post-partum your body is most likely switched milk production to an autocrine system. Which means your milk production is mainly based on how empty your breast are. If you don't breast fed regularly than that will cause your supply to go down. Long story short
just keep feeding on demand and your body should compensate if you have any dips in your milk supply. Trust in your body and don't worry too much (even though it hard) and you will be fine
If you have any questions please feel free to contact me. =)