I had unprotected sex trough out the month of may and then on june 8 i got my perdido on june i had unprotected sex as well with another guy and i am 18 weeks who could be the father ?

With two contacts so close together, the prime way to sort this out will be through DNA studies. There is a noninvasive method called the NIPP, which takes moms blood and that of the designated dad and can determine paternity. There are riskier procedures during pregnancy (amniocentesis) but many wait until after the baby is born to get DNA.

I want to clarify your statement. Were you supposed to have period on June 8 or did you really have a normal period or just spotting on June 8?