Only you can decide exhausted,but you do need a few facts at your fingertips to help your make a decision that is right for you.
It is hard work at the beginnig (esp. if another child on the scene but if you can ride through this then it suddenly will become a lot easier and a lot more flexible.You can go anyway at a moment's notice with a nappy in your pocket,have a hand free to snuggle and play with/read to your other child and be free of the hassle and expense of formula.
Contrary to what Ginge's MW told her,there are many quite worrying implications associated with bottle feeding which you are probably not even aware of.
My advice would be too go with the flow,sleep when the baby sleeps (whenever that is) and enlist help with everything else.
A chat with a breastfeeding counsellor may help too.Try the lovely people at Association for Breastfeeding Mothers
0870 401 7711
I speak as one who had every problem under the sun,but with good support and proper knowledge I pulled through,even when I was completely alone three weeks after ds's birth and moving house (my dh had to go back abroad to work).My dd was 3 at the time.
There really was light at the end of the tunnel and a few weeks in with both I was razzing around the world with my dh-something that would have been impossible with bottle feeding.