Teeth.... Help

Im almost 13 weeks. My teeth are fairly great condition before pregnancy. I take real good care of them. Even use enamel hardening toothpaste. Since being pregnant and having horrible morning sickness and throwing up so much my teeth have became horrible. Not to mention my calcium is low and ive tried everything to raise it. In the past couple weeks i have had 2 teeth in the back break. I really dont want to have them pulled. Has anyone else ever had problems like this? What can I do?