I'm in my teens and get regular white and sometimes yellowish vaginal discharge whenever I'm not on my period. Is this discharge najis and does it break my wudhu? As i find myself several times throughout the day having to change my underwear being unsure of whether it is najis or not?

Discharge that is regularly seen in women in normal days is paak and it does not break your wudhu. Discharge that comes after haydh which is dark yellow or yellow with probability of having blood mixed in it, that would be considered as haydh.