Hello,
If blood test for pregnancy is negative then it is unlikely that you are pregnant and these symptoms can be due to secondary amenorrhea. Causes of secondary amenorrhea include stress and anxiety, malnutrition, depression, overexercising, sudden weight loss or gain (obesity),thyroid disorders and hormonal imbalance due to polycystic ovarian syndrome(PCOS).
You should get all these causes ruled out from a gynecologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
I personally haven't but I have heard stories of women who just don't test positive for pregnancy even though they are. or other women who can't get a positive til they are 3 months along. so it's possible that you are. I don't want to get your hopes up because the tests are usually right but there are the women out there who don't fall into the usual category for those things.
I wish you and your hubby luck though :)