Pregnant? Late period?

So my period is only late by 1 day. Usually it’s early or right on time but I understand that periods can be super irregular when you’re in your teens.

The issue is, my bf finished in me the last couple times we had sex. I hadn’t realized I was ovulating when he finished in me

Not sure if I should be worried..? If I need to, I’ll buy a test or two after my period is supposed to end (if I don’t get it)

Also, if I am, how easy would it be to keep it a secret until after October 21st (my 18th birthday)? Because I need a parent at the doctors office with me until I’m 18...