Welcome to HCM,
Menstrual periods depends upon ovulation. If there is delay in ovulation due to any reason, menstrual period also gets delayed. Negative pregnancy
test indicates that delay was not due to pregnancy. Similar symptoms can occur due to other reasons also. Soreness of nipple is not a specific sign. First you should get semen of your husband tested. If report is not ok, consult a physician. If report is ok, consult a gynaecologist for your checkup. Further I want to tell you that fertilization of egg is possible only if you do intercourse nearby ovulation day. In a regular cycle of 28 days, ovulation generally takes place on 14th day, which can be confirmed by using Ovulation Prediction
Kit. To improve quality of semen avoid intercourse during other days. Both of you should take balanced diet.
Wish you good health & early conception,