I hate to say this, but my son is a toddler and I'm still tired all the time.
So long as you are nursing on demand (when baby wants and for how long baby wants), there's no reason your milk supply should suddenly drop in the ordinary course of events. But I would be wary of hormonal contraception - even the mini pill may interfere with milk production for some moms. And fwiw, the mini pill is not super effective. You may wish to explore a non-hormonal IUD, spermicide, barrier methods (condom, diaphragm), etc.
Generally, though, milk is produced on a supply and demand basis. The more your baby demands, the more is produced. You should not react to increased nursing by supplementing with formula, the increased frequency and duration of nursing is necessary to teach your body to produce the amount of milk your baby needs.
What I did was try to nap when DS slept. I also co-slept - if you're not comfortable having your baby in your bed, a co-sleeper or a "sidecar crib" (typically a dropside crib with the drop side removed, affixed to the side of your bed) will allow baby to be near you for easier nursing during the night.
In my experience, DH was also an integral part of "the team," and if your hubby isn't, now is the time to enlist him. I always said that I was responsible for input, DH was responsible for output. When DS was very young, he usually pooped during nursing, so I'd nurse for a bit, he'd go, DH would change him and bring him back, and I'd nurse him to sleep. As he got older and didn't always poop when he ate, he'd still usually be wet a lot during the night, so DH would change him before I nursed him. At any rate, the whole diaper changing process was delegated to DH so that I got a bit more sleep.