Some strains simply do not produce massive buds.
Cleaning up some of the smaller, lower duff will help. In gardening, common practice is to remove 'sucker' flowers, to allow the plant to focus fruit production on one single flower, making it larger. You can apply this idea to cannabis, to some extent.
What kind of branch support do you have? Tomato cages? trellis? stakes? This will help hold buds up as they ripen.
Happy growing!