Breastfeeding and giving formula?

Have any mama’s on here done this? I’m pregnant with my second baby and I want to breastfeed but want to give formula at night, 1 so my bf can help out and 2 I hated how I used to drift in and out of sleep while breastfeeding in the middle of the night! I never did that with formula so it eases my mind a lil bit! Any tips or advice on doing this? (I know breast is best but I only lasted a week last time so I’m wanting to use both in hopes of being able to do it for longer this time)