Click on "All BahnCard Services" under "My Bahncard services" approximately in the middle of the page.
This is where the webpage always switches to German for me. There is a menu item "Informationen zu meiner BahnCard" (Information about my Bahncard) that you can click on.
The page afterwards shows all the BahnCards you recently had, their validity, and should contain the information whether they have been canceled or not. "Abo" means "subscription". According to this answer on community.bahn.de, it says "nein" (no) below the "Abo" header if and only if you quit the subscription for your BahnCard.