I dont think its terrible at all to give your LO a bottle once in a while. My lactation consultant told me to wait and give my son a bottle until he was 3 weeks old to make sure that the breast feeding was well established, and to avoid nipple confusion. So it sounds like to me that breastfeeding is going well for you and your son, so I dont think it could hurt. Now if you plan on breastfeeding exclusively I wouldnt give him several bottles a day. But we would give my son a bottle a day to prepare him for when I went back to work, but then I ended up not going back, so I stopped giving him bottles (i got lazy )
I dont think it is selfish to want more sleep. i think it is something we all dream of!!
I will say that I am still not that comfortable nursing in front of people let alone family, and I've been at it for 6 months!! I still leave the room at my inlaws, mostly for the sake of my FIL! So dont feel bad about that!