Late! Help?

Okay. So I had sex with my, now ex, bf 3 weeks ago, as of tomorrow. The Saturday before that, I spent the night at his place but we didn't have sex cauze I was on my period, which ended on that Tuesday. So that next Saturday (3 weeks ago), we did have sex and I let him finish inside like always. But because I was so caught up in the moment and thinking about a million other things, I forgot that the week in between being there on my period and then finally having sex again, I had been off my BC cause I was on vacation and forgot. Now, I was supposed to start my period this Tuesday and I am late, which NEVER happens. How much longer should I wait before just taking a test? The last time I was pregnant, I took a test a week after I was supposed to start my period, but I'm super anxious and scared that I might be pregant again.

Oh, and if I am pregnant, I need advice on what to do! The guy I was seeing made it very clear, in the beginning, that he didn't want another kid (he already has a 5 yr old that he's raised alone). But I know that I have to tell him, I just don't know how. I really don't wanna upset him, cause he gets super angry sometimes, and I don't want him to hate me or think I did this on purpose or something. Which I SWEAR I didn't. Another kid is not exactly something I wanted right now.

Please, I need some advice and comforting words. I might be losing my mind over all this drama. :(