I have had sex with three different guys since september and i used protection all the time and i get my period normally but this month my period was abnormal. i spotted for one day and then there was nothing the next day and then the day after was when i

Do a pregnancy test: We do not know what protection you were using and inspite of the conraseptic precautions there is some risk with some methods including condoms.Since you did not have a regular period,i will suggest you do a in home pregnancy test and if negative wait for next period and if irregular or abnormal,then consult your Gyneciologist

Do pregnancy test: Get checked for STD'sparticularly chlamydia .An exam such as this will go a long way in ruling out or in infction vs. some physiologic cause for abnormal period.

What protection?: What type of protection are you using? Condoms decrease the risk of STDs better than other forms of contraception and are better than nothing for preventing pregnancy but are not that reliable so if this is what you are using a pregnancy test would be the first order of business. Other methods can also change your periods as can infections, stress, other medications, changes in diet, exercise, etc