Bike won't shift gears at all, please help!
So, before I explain the issue, a bit of background. I took my bike to college, but ended up not riding it much, so it sat outside for the majority of the academic year, chained to a bike rack. Because of that, many of the screws and gears and such have rust on them (I know, I'm an idiot for leaving it outside and probably ruined it, but I'm trying to fix what I can).
The bike is still ride-able and the chain moves okay, but the bike is stuck on the number 5 gear. (My bike has three gears on the left handle and 7 on the right). The left handle moves fine, although I've never used it much anyway, I usually just leave it on 2. However, the right handle will only move from 7 to 5, and won't even rotate to gears 1-4. In addition, rotating the handle from 5 to 7 does nothing to the gears, the chain stays on the gear that it has been on since I brought my bike home (I think it's stuck on gear 5).
I tried spraying some WD-40 on the gears, chain, and the shifting mechanism next to the gears, but that changed nothing.
So, while I can ride the bike on gear 5, I would really like to know if there is anything I can do to fix the gear shifting mechanism. I'm supposed to go on a bike ride tomorrow, so I can't take it to a bike shop (and my car really isn't big enough to transport my bike to a shop).
Thanks for any suggestions!
Edit: My bike is a Schwinn women's mountain bike, and the shifter is made by SRAM, if any of that helps.