Translation:I was a Physics teacher but nowadays I teach Philosophy.
You are correct. When a subject is referred to that you're studying, the only ones capitalized are the ones that are always capitalized, which is foreign languages and names of people such as, "I'm taking Russian and Shakespeare." A subject is capitalized only if it's the name of a specific course such as, "I am taking Chemistry 101."
כי מתי שחושבים על הדרך שהעולם הטבעי עובד, מתחילים לחשוב גם על המשמעות של כל החיים :)