Having done the same thing, the best advice I can give anyone who is serious about learning upright is to be
paitent. It may take a while before you feel like your really progressing, but it's worth it. It's not like the electric bass, where you can get a decent sound right away and play in tune, especially if you are using a school instrument.
I personally think studying classical technique with a good teacher (even if you want to play jazz in the long run) is invaluable, so you may want to look into that as well, if you are not doing that already.
Are you taking private lessons or are you in a group class? Private is always better.

Oh, and make sure you spend a lot of time with the bow. That'll help your intonation and even your left hand finger strength. Good luck, you won't regret it!
Pete