If you’re using the pill correctly then it’s doing what it’s supposed to do. Side effects like irregular bleeding, cramps, tender breasts etc are very normal on the pill, what’s important is that you use it correctly.
There’s no way to predict bleeding unfortunately, in any way.
If you’re not 100% comfortable relying on the pill only for contraception then use condoms, it’s not worth the stress of worrying about it.
I personally would be more concerned about STIs! (Unless you’re in a monogamous situation and have already been tested etc)