Pms or pregnancy?

My periods are sometimes irregular due to stress .. Okay so I was living with my aunt for about 3 weeks and I started to be on her cycle, which messed my period up and made it come earlier and be shorter. I moved back into my parents house & I ovulated on December 3rd and had unprotected sex that day. I also got really sick & had a bad case of strep throat a few days before my period and I’m not fully better. My period is now 5 days late, but I’m cramping & my boobs are sore. They were sore for about a week until my period due date then stopped hurting and they hurt Again. I’m also cramping but not bloated.. could I be pregnant or could it just be irregular because I was on her cycle a few weeks ago or because I was sick? I just need advice