Another option if it is bulk rather than weight that is the issue is to get vacuum bags for your clothes. You fill the bag with your folded clothes, seal it, and then hook it up to your vacuum cleaner. This pretty much halves the size of your clothing (but, unfortunately, does nothing for the weight)!
And also look carefully at your airline's baggage rules. Most, for example, allow you to carry a handbag, a thin laptop bag, an overcoat AND your carry on bag. It also makes sense to wear your bulkiest / heaviest clothing as you can always take it off if you are hot!