I keep a "Cancer Tracker" spreadsheet. It's got a row for each day of last year and this year. There are rollups that give total counts in various categories. If, for example, my therapist says "how many days did you feel sad last month" I can quickly get the answer. If my sexual health doctor says "What are the quality of your erections?" I can quickly get the answer. Here's what I track:

Meds: one column for each med and vitamin I take, marking it off with an X once it's taken
Appointments: lists any appointments I have, Blood Draw, Oncologist, Cardiologist etc.
Notes: general notes about the day if something unusual happens
Pain Level: 0-10
Exercise: what exercise I did that day
Dog walk: how many miles I walked the dog
Sex: did I have sex and/or masturbation (yes/no)
Erection quality: Good, moderate, weak
Orgasm quality: Good, moderate, weak, none
Sleep quality: Good, Fair, Poor

I'm a data analyst/business writer by trade so the spreadsheet is very elaborate and automatically color codes the cells red, yellow or green as well a tab with a whole bunch of pie charts looking at the data in various ways. It sounds like a lot but, other than the initial setup, it only takes about five minutes a day to keep it up to date and it really helps at Dr. appointments.