Hi Barrier contraceptive methods like condom if used properly and not torn or slipped during the sexual act are effective in preventing unwanted pregnancy. Apart from pregnancy, the delayed periods could be due to stress, emotional upset, change in dietary habits, hormonal imbalance, certain hormonal diseases like hypothyroidism, certain underlying medical illnesses, diseases of the ovaries or uterus. So, in view of the above get the home pregnancy test done first and then consult a gynecologist for proper treatment. Hope this answers your query.