Welcome to heathcare Magic!
If you had spontaneous abortions then there may be an anatomic or genetic problems.
If you are having fetal loss in 3-4 month then you may be having SLE like AUTOIMMUNE Syndrome
causing all this.
First of all you should visit and get examined by an experienced physician and get a physical examination.
In one cycle the chance of getting pregnant are about 15-20% after a regular unprotected sex, so obviously you need to have more patience.
Wish you a great health!