Should I be more concerned?

Autumn

Alright all you lovely ladies, I’m a little confused here. I am 20 years old, I am over weight and I just started tracking my period last month. Now I am apparently 18 days late, i have not had sex in over three months but fooled around with a guy a little after my last period, we did not have sex though. Just to be safe I took not 1 but 2 pregnancy tests and they are both negative, as expected. Is this normal?

I never gave me period much thought before I started having sex, I never could remember when it started, sometimes at the beginning of the month, in the middle, of the end, but I thought that as I got older it shifted slightly, it would make sense that it would change. I just never tracked how much it changed.

So my question is, is this irregular period usual for bigger girls? Is it okay to be irregular like this? Could it be that this one is just irregular and because I haven’t tracked it enough I should just see what happens with future periods? Should I talk to my doctor? Let me know your thoughts please, and thank you