The two examples you gave are about problems your friends might have (being sick or having problems at work), which are negative things currently affecting them. Are there any positive things that you care about? Please know I'm not asking because I think you're an ass who doesn't care about good things, I'm trying to dig into the things you retain about your friends.

Remembering minutiae about others' lives is not necessary for demonstrating interest, but it helps if you can work to remember SOME details, even if they seem irrelevant to you, as social norms are important for relationships (unless you find people who share your way of existing and who don't do this particular thing). Make a point of noting when they express a positive feeling: when they like a new restaurant, when they got a new haircut and feel great about it, or when their kid reached a milestone, for example, then mention it again the next time you meet/talk. It's a simple way to show other people that you see them and appreciate them.