I am 16 weeks pregnant now and my due date is march 23. i had my period around june 6th. i had 2 parnters one one time only in may 2nd and the other a week after since then and now. who could be the father?

Basics: Early estimates of due date (which are imprecise) and the overlap of two prospective males make this more a legal issue than one determined by the data you summited. You can have a test for babies DNA that circulated in your blood as early as 9 wks which has been accepted by the court for paternity lawsuits. By ~14 wks you can do CVS or 16 wks, amniocentesis for more accurate results.