PLEASE HELP! I NEED ANSWERS!

I recently took an Plan B because my boyfriend nutted in me. A few hours after I took the plan B I started to receive little to no blood at all. I had sex with him two days later and more blood came out after I had sex. It doesn’t feel like I’m on my period but it’s heavy enough to the point where I need to wear pads/tampons. I’ve been bleeding for 4 days and at this point I really don’t know what to do. I’ve also been getting headaches out of nowhere and I honesty think it’s the side effects of the Plan B....