Congrats on the new baby!
I don't think you have arthritis...I mean I guess you could, but for the pain to come suddenly like this, it rather indicates that it is not arthritis. I think you have what most moms get: a general post-partum fatigue. Your joints are trying to go back to normal as your hormones are switching over to the non-pregnant hormones, and you won't be as flexible as you were during pregnancy. Plus there's the fact that you are holding the baby quite a bit and picking her up and putting her down is going to make everything ache, not matter how light she is.
As far as I know, arthritis does not cause hair loss or tiredness.
Warm baths while the baby is sleeping, plus a supplement of Calcium and Magnesium should help with your tired and aching joints and muscles.
I don't know what your diet is like, so I don't know what you would need to add or take away besides the supplements I mentioned above.