Feeling crappy...

Don't worry.. Just look at the returned test and it will probably be painfully obvious where you screwed up. I got a 45(luckly he will drop the lowest) on my first exam but it was because I messes up on my negative powers. I'd say you just missed one or two things that were on a couple problems.. Oh.. And watch for extra credit opportunities! They are a godsend! Most professors will help you out if you show that your trying hard. they want you to succeed and so do we!