Sometimes before my period starts my lower stomach starts getting really sharp pains in it. When I get up to get something for the pain (like tylenol) I either pass out or feel like I am going to pass out. When I do pass out, and finally wake/get up, it causes normally loud noises to become silent and more quiet noises to seem as if they are really loud for a short period of time, and my balance to be off. It normally causes me to miss my period for that month. Why does this happen?