Menstrual cycles after pregnancy?

got a period 4 months after i had my son, but it seemed 'freaky' how the timing was just few days after i had , but i didnt note any discomfort, a month on almost, i have had strong cramps down there and at some moments the pain has radiated to my back which has been going on for over a week. today theres a white discharge but its not offensive at all! i dont know what to expect but the only thing that was remotely random was me projectile vomiting one gl of wine few days ago, which i hope is not related . what did anyone else experience with cycles after having a baby?