HELP! Any advice

I had unprotected sex last night and he came inside of me. This week is my fertility week and according to this app I’m at my peak for pregnancy I’m assuming. I do not want anymore kids. I’ve taken a plan b before but I just ended up releasing two eggs and ended up with twins. I was also told this morning that plan b doesn’t work if you’re already ovulating. Another major thing is I’m nearly 250lbs and I was told anything after 150lbs it wasn’t going to work so I wanted to know if there was anything I can take or do to prevent this before this goes to far? I’m considering ordering abortion pills but I’m not sure how that works if take to early.