Period is over a week late, but I just started a big change in my diet so could that be why? Or should I take a test?

I am obese and just started a diet as I am looking into bariatric surgery. I started after the New Year. I've been on birth control pills steady for the last 2 years and my boyfriend and I do have sex often, without a condom. When I was supposed to start my pills last Sunday, I didn't have them because my Dr. hadn't sent in the refill yet. My boyfriend was in the mood and I couldn't resist him so we had sex a couple times. My period was already late before we had sex.