If you leave a bulb of garlic in the ground by accident it will start to shoot, so you'll get a cluster of new bulbs trying to grow in a space far too tiny. If you plant the entire bulb (as I suspect you did?) then the same will happen. The individual cloves need to be separated off from the bulb and planted separately. Growing in a clump as your as they will not do well, so although it is late to separate autumn garlic now, I'd have a go, then replant each clove about 5in apart...and perhaps buy yourself some spring planting garlic now, separate this in to cloves and plant asap, as I suspect the autumn re-planted won't do as well as it could have.