Have a look into the virgin gut, babies are designed to only have breastmilk for as long as possible, its the best protection for their stomach and therefore protects them in the future against allergies etc.
the longer you can exclusively offer breastmilk, the best start you are giving your baby because as soon as you introduce a foreign body (in this case, formula which is a mixture of cows milk and wheat and whey powder) you are upsetting that balance inside the sensitive lining of the babies gut.
the best way i have had it described is that because we have such big heads, we actually have our babies at quite an early gestation compared to other mammals (who can walk and such like a few hours after birth) we are more like kangaroos, we have our young and then we grow them on the outside just as much as they have been grown on the inside
so its best to offer exclusive breast milk for as long as possible (even if its only a couple of months, but really three months should be the absolute minimum) rather than introducing foreign bodies.
get yourself a really good breast pump, the only ones i rate are the Ameda lactaline or the Medula In Style. they are expensive but for good reason. if you cannot afford that, go to your local sure-start center and borrow one for a while. they will understand
Once you are beginning to mix feed, you will be able to pump somewhat for the baby, it is law that the work place offers you somewhere personal, private and comfortable for you to pump milk along with a fridge to keep the milk. This has to be on their time NOT your lunch break etc.
Boobs change MASSIVELY after about six weeks, the first six weeks are there to promote milk production and for the baby to tell the mummy how much and how often they wish to feed, night feedings are essencial to this because the hormones are different at night. If you want to pump and feed maybe think of doing a feed for the hubby to give in the early morning? That way you wont be missing out on that fantastic milk production time and also getting that coveted bit of extra sleep.
after six weeks the breasts mature and begin to make milk on a more 'in need' basis. so actually we need to feed for as much as we possibly can for that first six weeks (NO feeding, NO Expressed milk - though you can start to store it) so that the baby and the mummy can teach each other.
Breastfeeding also creates hormones which allow our bodies to deal with less sleep more effectively, so dont be scared about getting a little bit less sleep than your used too. Also if you have the baby in the bedroom with you (reccomended by both the NHS and the WHO, you will find it is much, much easier to pick up baby and put it on the boob than it is for your husband to go down stairs, waking baby massively, making a bottle, cooling it (or warming expressed breast milk) and then trying to get baby (who by now is very awake) back to sleep.