Did you download anything else with it? Misclicked ads, other packs, etc.?
It may also be an external problem not related to the items. Does your computer have good CPU? You can find out how much by opening your Applications folder and double-clicking on the "Utilities" subfolder to open it. Double-click on the icon for "Activity Monitor" to launch it. Click on the "CPU" tab at the bottom of the Activity Monitor window to display processor-use stats and a live stacked-column activity graph.
If you're using too much CPU in other programs open, that might crash or lag the game, and if the game itself is using too much CPU try lowering render distance, disabling water reflections, turning off sound, or deleting some items if you have to.