Period??

I'm 18 and my period is starting to not follow it's natural course last month I was late by two days and my period only lasted three days out of four or five normally I took a pregnancy test cause I've had sex but always with a condom so either way it said not pregnant (thankfully I am not ready for children) and then I am due yesterday again but nothing no blood no period while I have all the cramps and headaches and usually over heating so my question is can our periods change course as we get older or is something wrong because up until last month my period has been consecutive and never change course after the first year obviously but if someone could give me insight I would really appreciate it thank you 💝💝