Here is a great link for you: https://www.cancer.org/latest-news/how-family-history-really-affects-your-cancer-risk.html
Hello~I can understand your worry about having cancer, it is a real worry. However, you don't smoke or drink and are only 20, so the chances of you having cancer are pretty slim. Possibly the pains you are having could be due to the stress of having cancer. I would eat as healthy as possible, drink at least 8 ounces of water daily, try to get at least 30 minutes of exercise at least 5 days a week. Have yearly checks with your GP to catch anything that might be starting.