I told my boyfriend that my doctors are doing tests on me for cancer and he hasn't even called. Why?

About a year ago my doctor found pre-cancer in me. They've been monitoring it, but lately I have felt that there is something wrong with me. I taste strange things like metal and see weird visions. My doctors are doing tests on me to see what it is. I've been with my bf for about two years now, but we've been on a break for about three months 'cause we were fighting all the time and he has a problem with honesty. He cheated on me last year and I gave him another shot, but he continues to be dishonest in even the little things. After three months of no contact he asked me out to dinner about a week and a half ago so I went with him. When we were out he noticed the gauze bandage from the IV from a surgery that I had two days prior and asked me why it was there and I told him that I had the surgery as part of the tests that my doctors were doing on me and he asked me a few questions about it and then acted like it was nothing. When he dropped me off at home he said he would pray for me and then never called again. I haven't really told anyone about this except my really close friends, my parents and him, but he's the only one that doesn't even call or seem to care. His dad died of cancer btw, but after he cheated on my he promised on his fathers grave that he would never do certain things again, but did them anyway. So I don't think he holds his father in very high regard if he promised on his grave and then went on to break that promise. He's known about the pre-cancer from a year ago and has never acted like it was even a big deal. He's been partying pretty hard these past three months (per his FB page) and hasn't stopped at all since I told him about my surgery. It's like it doesn't even bother him. I've always felt that he may be a narcissist. Can anyone help me understand what he's thinking?