If this is the "click" style laminate flooring, you should be able to reach under the baseboard of the gapped line of goods and pry on the end to close the gaps. This is...unfortunately...a trait of that type of flooring in a lot of cases.
Get used to it!
The best thing to do is remove the baseboards at the ends. Be sure the boards are not gapped anywhere, then squeeze a little gob of 100% silicone into the gap at the end of each line of goods between the goods and the wall. Replace the baseboard.
This will help to create a little resistance in the future when the boards want to move but at the same time it will allow more aggressive movement if necessary. Not foolproof but better than nothing.