Is it normal to bleed after i have ?

i bled on my first time that i had ive heard that that is completely normal :) .. after i lost my virginity i never bled again until i got into a nother relationship ive had after that and i never bled until this last time that i had , i had and there was no pain or anything .. after i had i bled and it lasted like a regular period and after that my period came again ? what does this mean ? why does it happen ? i really need someone to tell me if this is normal :(