Hi Laura,
The best sure fire way to set up a new sequence correctly is after you create it drop a piece of footage from your bins into it. you get an alert along the lines of “this sequence is not the same as the footage you are using would you like to change it?” Hit yes and your good to go.
Now that you have a sequence set up properly and 1 piece of footage in it, copy the footage in the old sequence into your new sequence. Now you need to correct the distort that was applied by putting it into a incorrectly formatted sequence. The best way to do this is copy attributes from the first clip you put into the sequence, then select the rest of the clips in the sequence and paste attributes. Select Distort from the pop up menu. This should get you back to where you need to be.
-Andy