test?

My Bf and I have had unprotected sex 3 times this month...and last night, I KNOOOOW he finished inside me. We're not trying to conceive but we're also not avoiding it. It's kind of like if it happens, okay. If not, then that's okay too. My period was July 9-13 and before that, it was May 20, and the one before that was Feb 2...its VERY irregular so idk when my next period is due. For some reason, I'm excited about taking a test, but when should I test?