should i be worried?

My boyfriend and I had sex dec 4, and we switched between unprotected and protected. We first tried unprotected and we got scared so he put a condom on. We did that for a couple of days and stopped. Then I got worried so I took a pregnancy test and it was negative. The following week, dec 13 we did the same thing. Switched from unprotected to protected. He didn’t cum inside me. Like at all, but having sex, protected or unprotected, will always have a chance of pregnancy. Last time I had my period was Nov. 18. Last week I started to feel my breasts being swollen, like how it would be before period. And yesterday I started feeling nauseous, but I think it’s bc I’m anticipating my period. Today is Dec 18, and I still havent gotten my period. I’d have irregular periods, but should I be worried?