One more thing you might want to be aware of is that having sex can also alter your period. Personally I'm on birth control and usually get my period on the Wednesday or Thursday of my 4th week but if I have sex on the weekend of my 3rd week going into my 4th week I will get my period earlier in the week such as the Monday or Tuesday.
I would recommend using contraceptive birth control and condoms. Birth control pills are great because they not only prevent birth but they also regulate you where you can expect your period approximately the same time every month and monitor it.
Yes it is totally normal to bleed after the first time, it is from you hymen (thin layer of skin) being broken. It can last a couple minutes to a few days and may happen more then the first time you have sex.
TMI here but I lost my hymen through "manual" stimulation (fingering) and I bled the first 5 or 6 times.