I had sex three days later my period came after my period was over i had sex with another guy who is the father of my baby?

Too close to tell. Once a 2nd potential father enters the picture it becomes a legal issue where the true father gains certain rights/responsibilities. You can receive a paternity study as early as 8-10 weeks on maternal cell free fluid (NIPS) that can provide evidence that will be accepted in court. Test or not, over time the answer may or may not become quite evident.

More than likely it is the guy you had sex with after your period. As Dr. Ferguson advised, you can get a prenatal paternity test to settle the matter. Pre-natal Paternity testing: https://americanpregnancy.org/paternity-tests/non-invasive-prenatal-paternity-test/