Don't feel bad, you're not alone. I think a good percentage of people here are guilty of taking things a little too fast when they start up, especially after getting advice from the LFS.
When I first started, I had an established sand bed leftover from the previous owner of my tank, added 4 pounds of rock, let that settle for a week or so, and then went and got 8 more pounds of rock, two A. Ocellaris, and a peppermint shrimp. I added them all to my main tank on the same day. That bit of poor judgement resulted in a good 3 months of QT for my clowns, a full month of which was very stressful in a "Are they gonna be alive this morning?" kind of way.
So you're having a rough start...try to learn from it, and don't get too discouraged on the hobby. The big take-home message here is from now on, try to do most of your research on your own. This website, among many others on the internet, are great resources and have a lot of information to help you out.
Let us all know how everything works out for you...best of luck!!!