Oral contraceptive pills. Prblms!

4 months ago I use pills instead of condoms ..with 2 person's..im very healthy person with regular periods..I afraid about STD and search many qns in net ..no solution available.. I h'v doubt abt any further prblms regarding these participation ..my qn is STD r transmitted by only effctd persons i mean who r already effected with hiv ,herpes, gonorrhea, syphilis,...or with healthy person's also it may transmitted?.ND my 2 nd qn is i exposed with 2 person's drctly without protection so through semen any other diseases leads any infections..or more than that like HIV,aids,cancers,..because these are very dangerous without any previous sympots to diagnose..within these 4 months i have no sympots abt my genital organs..bt i obsrv any related sympots is further exposed ..upto now no dangerous sympots ..bt anymore means i inform to you and give previous suggestions ..plz give me best solution to keep me in safe zone