Breast Milk Or Formula Milk

I am a new mum, to a 10 days old baby. I know that in the beginning, the milk supply will be little and if you continuously nurse your baby, the more milk you produce. but i am getting little milk so far, and i am afraid that i haven't been feeding my baby well. so my doctor suggested that i should give my baby formula milk, just to add on to my breast milk so that my baby is well fed. i am getting tired of pumping my milk out and seriously considering to just stick to formula milk. i am seeing how these few weeks will go then i will decide whether to keep pumping or stick to formula. cause it was after giving my baby formula milk, my baby has been pooping and urinating well, even grow heavier. so my question is, which is better? should i continue giving my baby the breast milk?