Keep it simple, sweetheart.
Bass can be real simple and still sound good. An example of how simple you can get: Find a note that sounds good with what the primary instrument is doing and just thump a rhythm on that note. You can actually get away with this for a while.
Or, find the note that has the same name as the chord the guitarist is playing. Call that 1. Now find the note that's on the next higher string, two frets higher than the first note. This is 5. A lot of good bass lines are built around 1 & 5.
Remember, your most important job is to synch up with the drummer and nail down the groove. Fancy stuff can come with time.
The best compliment I ever got on my playing was when a jazz pianist said "Once she gets hold of a groove she don't ever let it go." For me, that's what bass is all about--the groove.
Oh yeah, do yourself and your band a favor: buy a metronome and USE it--use it every day, even when you aren't playing your bass, just slap your leg to it.
When I first learned I didn't have a metronome so I practiced drumming on the steering wheel in time to the windshield wipers and the turn-signals. (NOT while I was driving!!!)
Hang in there and remember k.i.s.s. 
