I'm freaking out someone please tell me what's wrong with me

So I got put on the shot September 12th and I started my period October 4th and it lasted until the 15th and I had unprotected sex on the 18th and he accidentally came in me and now I'm bleeding a little bit and I'm not sure if it's random sporting from being on the shot or if it's implantation bleeding and I'm freaking out and I don't know what to do