The symptoms for pregnancy vary considerably. Some women experience a lot of cramping while others have none. Just as some women experience morning sickness and about 30% do not. One symptom that I've heard is a very good indicator of pregnancy is an abundance of cervical mucus, especially near the end of the cycle.
Have you ever considered charting your temperature every morning? I started this about two months ago and have learned so much about my cycle. I can verify that I have O'd, and a lot of women can tell that they are pregnant before a HPT turns up positive -- all because of their temperatures.
Good luck! I hope to hear good news from you soon.