For years, I have filed as Head of House.
This year i goofed and filed single.
I fully support my household.
Should i fix this? Will it result in a bigger refund?
So long as you have a qualifying dependent and satisfy the other conditions to be Head of Household, you can change your filing status.
Changing your filing status to Head of Household will likely reduce your assessed tax (see the 2018 tax brackets at https://turbotax.intuit.com/tax-tips/irs-tax-return/current-federal-tax-rate-schedules/L7Bjs1EAD).
It is not guaranteed to increase your refund, because it depends on what tax credits you have taken, but it's worth the try.
Since you have filed, you will have to amend your return. Please see this TurboTax FAQ for how to amend your return with TurboTax - https://ttlc.intuit.com/replies/3288565[Edited 4/10/2019 9:45 am CDT]