need advice for sick fish!!!!!

Lake Forest CA

Description

i have a 4 year old goldfish. lately he has been acting weird, laying on the bottom and not moving until someone walks by, i went to pet store and they said his nitrates and acidity was high so i did a 90% water change and added bacteria starter to the water and also some sort of alkaline salts that the pet store suggested. it’s been almost 2 weeks now he’s still sitting on the bottom. and now, today, i noticed his eyes are bulging out of his head! and he is a normal goldfish not one of those bulgy eyed ones. the last pic shows his usual eyes before the bulging began. i am not sure what to do i am super concerned and if anyone knows about fish please please please let me know what i can do. i really want him to live as long as possible. at first i thought he was depressed as he has no friends in the tank because he is aggressive, so i added more plants for him to interact with but it didn’t help he stays sitting on the bottom. also the tank is 35 gallons and i have removed all of the plants just in case he hurt his eyes on those.