Unfortunately, you'll have to redo it. Like Mercia Collins said, you might have been skipping stitches. Try counting stitches for the first few rows to make sure it is the right number before continuing on to the next. Keep counting until you get the hang of it and just count every so often to make sure.
Whether you have to work on the chain from the previous row depends on the pattern. If it states that you count the turning chain as part of the stitch count, then you have to work on it on the next rows. This is usually applicable if your stitches involve hdc, dc, or tr. If it does not count the turning chain as part of the stitch count, then you don't need to work on the turning chain.