38 Weeks and Closed Cervix

38 weeks preggy now and still closed pa rin ang cervix. Pina inom ako ng OB ko ng Primrose Oil for 4 days 3x a day. It's my first day of taking the meds today. I'm worried kasi ayoko talagang ma CS. Till now, wala pa rin akong nararamdaman na mga early signs of labor. Medjo worried na ako. Possible ba na by next week may effect na? By the way i'm a first time mom so i really have no idea on what to expect.