I have trouble crying too but, it's normal to cry. It makes you feel better and relieves stress and it's good for you. People who don't cry are more likely to have health problems. If you want to cry in private then, go somewhere private and listen to sad music or watch a sad movie. Things like this can help you to cry. Also if you believe in God you can talk to him the same way you do to anyone else. The relief from expressing what is on your mind and in your heart can bring you to tears too. When the tears and sobs come give yourself over to them completely and let it flow from you. You will feel so much better.