Question please help

Okay I’m very confused. Please help.

So based on my own knowledge before I took birth control pills, my only indication that I wasn’t pregnant was me getting my period every month.

I’ve read that when you take birth control, you don’t get your normal period but instead you have what’s called a withdrawal bleeding during your placebo pill week.

Now I’ve been on birth control pills for 2 months and I get my withdrawal bleeding on my placebo week.

My question is how would I know if I’m pregnant while on birth control pills? Should I take a pregnancy test every time I end a pack? Or does having withdrawal bleeding on the placebo week indicate that I’m not pregnant?