Irregular periods lately

Alia • Hi🤗 I'm 18 and am just going this app works well🙂

My period was pretty normal for the last 2 years or so. About a 26 day cycle Only off by a day or 2. But for the last 2 months it’s been very irregular. My last period was 12 days early and this one was 7 days late. I’m not under much stress. The only thing I can think of is that I just started working out again often. Is this normal when you start working out more?