Should I ?? Help please...

So according to the app my fertile days are 18-24 of June which I just passed that window. Well Sunday (June 25th) morning me and my husband had unprotected sex which we never do to avoid pregnancy. But he was a bit drunk I was running on 3 hrs of sleep so one thing lead to another. 
My question is, is there a high chance of getting pregnant? I'm suppose to start my period July 7.
I did buy the plan b pill but I've heard you'll have a very irregular cycle for a while.. 
I'm suppose to be going on a Vegas trip in August I don't want to be bleeding the whole time I'm out there 😩 
Should I take the pill or just hope I'm not pregnant??