When to test?

My fiancé and I are ttc for 2 months now. My periods are usually regular except for last month I was a week early. Going by that period I was supposed to start last Friday the 13th. My period didn't come so on Monday the 16th we did two Clearblue tests, one digital and one regular. Both came up negative and Glow moved my expected period date to the 21st of this month, which fits when I would have regularly started if my period wasn't late last month. I guess my question is, should I wait to test again or just go ahead and test again? I am 37 days into my cycle and going nuts!