Hello Apurva. First of all the black line that you are describing is called linea nigra and disappears a few weeks or months after delivery, so do not worry about it. Dermadew is an aloe vera based moisturising which helps in preventing stretch marks during pregnancy, if advised by your doctor. It has no effect in clearing any marks, but you should still continue this as your skin will require all the hydration and moisture it can get. Abstaining from sexual intercourse is advised for a minimum of 3 weeks after delivery, but only as yours was a c-section. For normal vaginal delivery the duration can be longer. Other than the use of condoms I would advise birth control pills which can be taken on a daily basis, or the morning after pill which can be taken within 72 hours after unprotected sexual intercourse. But is most effective if taken within 24 hours after unprotected sexual intercourse (98 % effective). You could also consider the insertion of an implant into your arm which is also an effective contraceptive. Please consult your doctor for the same. Hope this helped you Apurva. Take care.