If you are bfeeding and have the bf established - over b weight, plenty of poopy and wet nappies a day etc etc - I would recommend intro'ing a bottle of ebm for the df. Even the sleepiest baby (like my DS who CANNOT wake up even these days once asleep) will suck much easier on a bottle teat.
I successfully fed both my kids from birth a DF (sometimes they would wake just before but by and large we were df'ing successfully by 2 weeks old) - one with a bottle from 2 weeks and one always off the breast.
And no, not all bf babies wake every three hours at night - and even if they do, if you intro the DF and use a bottle, your DH/DP if available could do the DF so that you could get 6 hrs sleep ish or even more.
Of course, I would only recommend these things if feeding is going well, baby is gaining nicely and you have no issues with supply.
HTH and hugs xxx