Should I switch from SSI to SSDI ?

I have been permanently disabled since i was 18.
I started working part time a few years ago and in a year and a half i will have enough work credits to switch to ssdi.
The good thing about that is they stop taking money away from me based off how much i make.
What scares me though is if they base they ammount of ssdi i get a month off the amount of money i have earned, thats not going to be a lot of money.
I have to walk a tight rope where i cant earn too much or too little.
But by doing that and then switching to ssdi, am i going to get less money a month than i would just staying on ssi?
And what happenes to the SSA i get from my father?
Its scary and i kinda just want to quit work over the fear of making things worse.
Any insight you might have would be appreciated.
Thank you.