Is a person more likely to get cancer if they have insomnia? been sleeping only about 4 hours a night for about 7 weeks. what is this doing to immune system? if blood work is normal, does that mean immune system probably ok?

No evidence of link: between insomnia and cancer. Please check this article http://www.mayoclinic.org/healthy-lifestyle/adult-health/in-depth/cancer-prevention/art-20044816?pg=1

Sleep is important: Why do you have insomnia - you can ask your physicians, see a sleep specialist. I am uncertain you have an immune problem.

Yes over long term: You are right that chronic lack of sleep increases risk of certain cancers such as breast cancer and colon cancer, though it is unlikely that 7 weeks is long enough to cause this. It will reduce immunity but you can enhance immunity with a healthy diet, good multivitamin, extra C & D, exercise, stress reduction and herbs like andrographis, ashwagandha and medicinal mushrooms. See comment for more:

No relationship: I have never found any relationship between a sleep disorder and cancer as a result. If you are concerned about immune system integrity, see allergy and immunology, as some more direct testing can be done.