It's different for everyone and is a combination of things - physical trauma, physical exhaustion, lack of sleep, emotional "worn outness" and potentially low oestrogen levels. If you are bfing you are more likely to have low oestrogen levels for the first few weeks after the birth. There is a cream you can use to help with this. It's best to speak to your health professional to find out more if you are interested in doing something about it. It does get back to normal - after the first couple of months for some, after the first couple of years for others - it all comes down to you and your own body and situation.

I always found the hormonal contraception was an issue too.