Opinions please?

Sooo. I had my LO a few weeks early in July. Got my period right after i stopped bleeding in August, and got my period in September. I just went to look and see when my period was due on here and it says im 15 days late.

We had sex in September during my projected fertile time (once, and he pulled out) a week or so later I had some spotting that i just assumed was a light period. Should i go buy a test or can i be irregular even though the last two period have been the same week??? 😬😬😬😬