I knew the end of my menstruation by inserting tissue and checking internally rather than the external area.My usual cycle of menstrual discharge lasted 7–8 days (according to my previous way of verification) blood, pink/brown and yellow, sometimes complete dryness. I get now that the Maliki way involves checking outside and what I did before was likely a compulsion from when I had purity waswas. I don't know when I became pure in each cycle.Should I make up a number of prayers from 2 years

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, ﷺ, is His slave and Messenger.

You are not obligated to make up any of the prayers, because the default ruling [in your situation] is that your obligation has already been fulfilled, and because several scholars held that one who abandons the prayer, or a condition or pillar of it, out of ignorance is not required to make it up. This is the view adopted by Shaykh al-Islam Ibn Taymiyyah, and it is permissible for you — being one who suffers from waswas, as you mentioned — to act upon his view in particular. Going forward, you should determine dryness by examining the outer part of the vulva, which is what becomes visible when sitting to relieve oneself.

Allah Knows best.