Late period

So I'm about 6 days late, which I'm normally always late when having my period, but not this late. I'm having symptoms but they come and go. The last time I had sex was almost 3 weeks ago and my boyfriend and I used a condom and we always do. We both know that nothing went wrong with the condom, but I'm still just so worried. Also in the past week I drank a lot because I was on spring break and the last time I had drank was New Years. Could that be why my period is late?