Well, you don’t NEED to start applying for graduate school this fall. There’s nothing written saying you have to go to grad school right out of undergrad, and lots of people don’t.
With a 2.5 GPA, I’d say you don’t have enough time to retake classes to make any meaningful difference between now and December.
I’d agree with the advice to take some time between college and grad school. Maybe work as a lab manager if you can get a job in that role, or doing psychological research and/or clinical work (not direct, of course, but assisting) in between. Having that kind of experience - and maybe taking a few graduate-level classes - will help you overcome that 2.5 GPA in a couple years.