Hi
you're welcome ... its public after all ;-)
myself I totally despise most apps (and I'm a software developer) for these reasons (
link) and the situation has only become worse since 2012 when I wrote that. So my most sincere advice is "use a spread sheet" and store that on your computer AND also on a cloud storage.
I use a spread sheet for my INR tracking and if you wish I am happy to asssist you to set one up. Sure a piece of paper works but I am certain that you'll find (for instance) graphing stuff is critical to understanding what's happening and making decisions, and no piece of paper does that without you making a lot of effort. I use Excel but you can also use Open Office (now called Libre Office) across platforms (Mac, PC, Unix) and its free.
Best Wishes