First of all don’t get discouraged. Most musicians going into college have at least 3-5 years experience playing music (with many that have close to a decade) through combinations of private lessons and ensembles (school related and otherwise). I’ve been in situations where I’ve had to compete for spots where my competition had nearly twenty years of experience despite being the same age as myself. The simple fact is that this business is tough. There will always be a player who has more chops, better intonation, and sight-reading skills.
So what are you to do?
Well first, stop comparing yourself to other players and focus on what you want to accomplish and how you will get there. If you let other people be your ruling factor, you will never develop a voice of your own as a musician. Look at Roark. He couldn’t have gotten anywhere with his career if he was always comparing himself to other architects.
Second, realize that being a musician is a huge commitment of time that will rule over everything else in your life. If you’re looking to have fun and party a lot and maybe hold down a job part time while going to school, you will quickly find yourself overwhelmed at the amount of practice time you need verses what you actually have. Outside of your peers in class, you realistically cannot have any sort of a social life. I would also advise against a job that requires more than a 15 hour per week commitment unless your financial situation dictates otherwise. If you must work, a campus job is the best option in this case, as they must work around your schedule.
Finally, realize that you have some work to get you to the level where you can handle being in a college jazz ensemble. To be frank, if you can’t follow a walking bass line from sight, you’re not ready to be in a college level jazz band.
To help with a walking bass line, buy yourself a copy of the Real Book in C. If you’ve listened to a lot of jazz, you’ll recognize many of the charts as standards. Just practice reading through a couple of charts each practice session. Since the bass lines aren’t written out in most cases, this will teach you to read by following chord changes.
Now as far as sight reading written material, counting is everything. If you have to make a choice between getting the right note and the right rhythm, go for the rhythm. By the time you find your right notes, the rest of the group is somewhere else and you’re lost.
I would also recommend studying music theory and analyze the playing of bassists you like. If you feel comfortable with it, you should transcribe their solo’s as well as this can be helpful in understanding what they are doing and has the added bonus of improving your music reading ability. It would also serve you well to find a drummer and a pianist/guitarist to read through charts. That way you can get comfortable working in a rhythm section and take what you learn back to your ensemble. Plus, if your group becomes good enough, you can play side gigs for money.
If that seems daunting, you might want to concentrate on your gen-eds first while becoming more sure of yourself as a musician. This is a lifelong journey so be sure to enjoy it. Although you will be quite busy for the next five-seven years (as if any music major gets out in four ha!) you should as much as possible stay connected to that which made you want to become a musician. If nothing else I hope the following video helps takes the edge off of everything.
https://www.youtube.com/watch?v=3KANI2dpXLw