pills and your period.

I have been on the 3 month pills for maybe 2 years and I really liked only having my period 4 times a year. However, I ran out beginning of January. I am already 5 days late on my period and I was wondering if it was because my body needs to readjust to having it monthly again. Has this ever happened to anyone and is it normal? ( I have ruled out pregnancy since my test came out negative last Friday)