Irregular periods and pregnancy test

I have a very irregular period, but today marks cycle day 41. (I'm usually 30-40 days)
Im worried that I may be pregnant because this is definitely on the longer side and I had unprotected sex on cycle day 6 and ~12.
I don't know how to figure out when I'm ovulating when my period isn't the typical length so I don't know my changes. 
I bought a home pregnancy test but I don't know when my levels would be high enough to show up? Would pregnancy register at this point?