PLEASE HELP!!

Okay so last month around the end of the month, me and my boyfriend had sex, he went raw with no condom and claims he pulled out but he didn't cum when he pulled out, he said he felt like he pulled out on time but he didn't feel like he orgasmed. Now I am experiencing nausea , back pain, tiredness, and cramping. I am supposed to be on my second day of my period but I don't think I'm on my period. 4 days ago I peed and when I wiped myself I had a little bit of blood so I put on a pad but later on when I checked I wasn't on my period, the pad was completely clean, then the day after the same happened except I kept bleeding. It wasn't red though it was pinkish brown and I only had I use one pad for the whole day that's how light it was. It's been like that for 3 days now. Please help me with ideas on what it can be. This is a picture of my pad and how it looks like , I'm sorry if this is too disgusting I'm just kinda scared right now