At the moment, I use Apple Health for storing step counts, weight and BMI. I have tried to use the cycle-tracking function but it’s a bit clunky and I couldn’t be bothered with it after a while. I keep a basic summary of my medications on there as well as my blood type (when I was pregnant, the blood type was really important as I am negative and the baby is positive, so any early labour would have required a shot to ensure I was able to carry subsequent babies without issue).
I wish data was easier to get out of Apple Health!