late period

Ok so i finally decided to post this on here. So my boyfriend and I have had sex a few times over these past 2 weeks. We always use condoms but I'm not on birth control. My period was late by 4 days (similar to last month probably due to the plan b I took). I assumed that my period was coming a few days ago because I always get acne on my chin. Today I had some spotting and cramps. This lead me to believe that my period had finally started but... there hasn't been any blood. Obviously I'm pretty concerned and any feedback is helpful. 😅