Miscarriages are a very common problem; up to 20 percent of all clinically recognized pregnancies result in miscarriage, and a much greater number than this are "silent miscarriages" where the pregnancy was never noticed in the first place. Most often, the causes of miscarriages are never known, but people who suffer from repeated miscarriages as you describe should have a further evaluation by an OB/GYN.
A number of factors have been shown to increase the risk of pregnancy loss, including maternal smoking, drinking, or drug use, a history of prior miscarriages, or advanced maternal age. In the absence of these factors, an underlying medical condition may be responsible. These include anatomic problems with the uterus, such as congenital (since birth) malformations, maternal endocrine problems such as hyper or hypothyroidism, and maternal hematologic (blood) abnormalities such as the antiphospholipid antibody syndrome (a rare disorder leading to increasing blood clots). An evaluation for causes of recurrent miscarriages is a comprehensive process involving an in-person consultation with a doctor
who can ask you specifics about your medical history and that of your family, your habits, and potentially order blood tests or other studies.
Recurrent miscarriages warrant further evaluation, and if you desire to become pregnant, I urge you to seek an in-person consultation with an OB/GYN as soon as you can; they may be able to establish a diagnosis that will help you carry a child to term in the future.