fainting episodes that begin with severe headaches...

I am a 29 year old woman that is slightly overweight. Over the past several years I have been having fainting episodes that begin with severe headaches and chest pain that begins in the middle of my chest and radiate down my left arm. I am also told that after I pass out I sometimes seem to stop breathing for several seconds and have a seizure. After I wake I am often confused and extremely tired. The last time it happened my doctor diagnoised it as a TIA and ordered tests to be done. A mild arrythmia was found, but I am told that my heart is healthy. However, it was also found that suffer from anemia and low TSH. The doctor does not know what is wrong and has sent me to several specialists and no one has an answer. They have ruled out panic attacks, heart disease, and epilepsy. Yet the same symptoms seem to still occur every so often.No one seems to have any answers. What could this be? Even my own doctor does not seem to know.