Sex during placebo week?

Is it safe to have sex during your placebo week? I take a combination pill and had sex with a condom the day I had to start a new pack. The week leading up to sex I was on my placebo week. I have never missed a pill but sometimes I have take it a couple hours late. Also if I took Plan B in November will that throw off my cycle and cause a higher chance of pregnancy? So basically does having sex during your placebo week put you at a high risk for pregnancy? I used a condom so should I be worried? This was my second time having sex so I’m still new to this and kind of nervous..

also had sex two weeks ago and I feel sore down there right now for some reason... normal?