longer cycles

Hey ladies is it normal for your period too continue being later and later in the month
I used to be super on the dot since I can remember it was always 19-22 alway never more and now on December it moved to the 24 and last month the 26 and this month I'm due for it tomorrow. Is there any explanation for that or am I just over reacting? Also I'm not on birth control or any medication and I highly doubt I'm pregnant because we don't have sex but yea.