First of all: I applaud your ambition and enthusiasm - the most important thing is to always keep that going as much as possible.
Anyhow - I think you have good answers here already, but this is too long for a comment, so:
im supposed to be doing about two and a half hours of practicing
Who said that's what you're supposed to be doing? That's a long practice session focusing just on the technical aspects of playing for a lot of musicians, no less a relative beginner.
is there such a thing as overpractice?
Yes, there is such a thing. Pushing yourself too far won't help you, and it might hold you back: You're liable to get sick of it/burnt out, and slide all the way back. You may not see it yet, but it happens.
Burn-out is not uncommon, and it can sometimes be abrupt: One day you sit down to practice and you're just not in the mood - you can't get it going - you start to feel depressed and discouraged - you'd rather watch TV or go out with some friends - you feel as if life is passing you by and you're wasting your time with music - never making enough progress... Finally you put down the guitar and don't touch it again for another 10 or 20 years, or maybe never.
Keep in mind: The rests are a very important part of the music.
If you really believe you need such a long practice session, at least break up your routine by playing along with records and experimenting - things that you can enjoy. Practicing is usually not fun - it's work. But you can mix in some fun to make it easier. Still, it's highly questionable if you need to hold such long practice sessions, as the other answers have stated.
Am i underperforming
There is no objective way for any of us to know that. Who/what is going to determine if you are underperforming? Underperforming compared to who? Compared to what? There is no set timetable for anybody's progress. It depends on your goals, your talent, your available time...
If you were Franz Liszt, you might be "underperforming" if it took you more than an hour to play through a whole fake book on the piano. If you were me, it would be great to do it in a month's time (on guitar or bass).
I see in the comments that you can't get a teacher right now. But you can get books that have methods and lesson plans that give you focused exercises, milestones and goals to achieve over time, and a reasonably paced plan for moving forward in doable steps. I cannot offhand recommend the right book for you (I've bought any number of books that I never use, and two or three I use all the time...) but do some research: The reviews on Amazon from real people about instruction books is a good resource. Also try googling for information and material.
Above all: If you are indeed as serious as you sound, do whatever it takes to get yourself a decent teacher (research that too), and meanwhile do talk to your musician friends and try to get help and feedback from them - maybe play with them sometimes. It's very difficult to feel good about what you're doing or know if you're really making progress, without feedback and help from other musicians.