Ay, malapit na talaga ang due date mo! Hindi ako personally na-try ang primrose (I was induced with Pitocin), but I have a few mum friends who did try evening primrose oil close to term, one swears it helped soften her cervix and went into labor within days, pero honestly ang iba naman, walang bigyan agad eh. Since you're already 38+ weeks at may insertion na ng primrose, I'd say follow up closely with your midwife on the cervical changes at makipag-coordinate sa kanya on timing, kasi every body talaga ay different. Best to check with your OB or midwife din kung effective na ba based sa your specific situation!