It's really very frustrating when you're trying so hard to conceive and can't seem to have a positive pregnancy test. Well, have you got yourself checked by your doctor? If not, please get it done. There may be numerous reasons why you are finding it difficult to conceive. Some of the commonest and treatable causes are thyroid problems, hormonal imbalances- PCOS,etc. So you also need an ultrasound to rule out any anatomical defects. Your husband also needs to get himself checked up.