When To Test

I'm on the pill right now, it's my first month. My boyfriend and I have sex without a condom pretty frequently, but a week and a half ago he came inside me for the first time without one. I had been on the pill only a week, and today I was feeling a little nauseous in the morning. It's actually normal for me, just a little irritating, so when I complained about it he got a little worried. He asked if I would take a test if my period doesn't show up on time, and I agreed so he wouldn't worry as much. I have very irregular periods and this will be my first one while on birth control of any sort. When would be the best time to try a pregnancy test?