I have had dizziness, nausea, and fatigue off and on for about a month now. i suffer from migranes. what could be the cause?

Many possibilities: You could be suffering from one or more illnesses including sinusitis, type 2 diabetes, heat exhaustion, anemia, stress, or drug side effects. You need a complete exam in a clinic as soon as possible to rule out these and other illnesses. The sooner you are properly diagnosed and treated properly the better your chances of recovery will be. I wish you well with your health!