Body lice may be prevented by bathing regularly and changing clothes. Body lice live on clothing, not on the body. Washing clothes in hot water (130 degrees and higher, check the water temp) will kill the lice.
Some people have an allergic reaction to the bite which lasts 7-10 days. Do you continue to have the lice or perhaps suffering from an allergic reaction.
Merck & Co has a drug 'Ivermectin' to treat lice when various topical treatments do not work. Ivermectin is a once daily pill. Speak to your Doctor. Good luck and I hope you feel better soon!

