What Causes Headache And Nausea?

I have bad headaches everyday. I sleep on time and sometimes I don't get sleep at all because of so much stress. Sometimes I have nausea and I feel that there is something wrong in my brain. I tend to forget things which I plan to do before 10 minutes. I do not have any insurance so I don't want to go tot the doctor but this is getting worst day by day. What do you think is the problem ?