Brake problems

1997 landcruiser 98000 miles
Just started having to push the brake pedal all the way to the floor to stop. Sometimes it stops as normal and sometimes you have to push the pedal all the way down. I do have a level in the brake fluid resovoir. Any help please

quite likely air in the system. take it to a shop that does free brake checks. they want you to pay them to fix things, so if its even remotely a possiblity they will list it and say you NEED it. after that, low pads (replace) or failing cylinders, master or slave