It might be a problem, because in the future you will need to communicate your ideas to others. Because we have no way to see what's in someone's head, the sketch is how the idea is conveyed to the world. Remember, you only need to communicate the idea, the sketch need not look like DaVinci's Mona Lisa. Some designer sketches are very sketchy and un detailed, other put in every seam, fold and button.
Instead of artistic sketching perhaps you might be better served by technical drawing, that is, draw out your garments similar to how they would appear if laid out flat. Here's an example of a technical drawing from the burda patterns website: http://www.burdamode.com/106_A_Blouse,1270777-1000019-1508211-1508216-1508355-1508357,enEN.html?displayValue=Update&taghandler=OnlineArtikelContentTaghandler
Some designers do only this type of drawing, one buddy has dispensed with heads and arms altogether and draws hangers rather than people.
In drawing or any type of art, practice makes perfect. The more you draw, the better you get. Comic book artist Dave Sim put it quite succinctly when he said "You need to make two thousand bad drawings before you can make one good drawing." Don't get frustrated by you two thousand bad drawings, learn from each one. Here's a website aimed at fashion illustrators rather than designers, but it will help you with the nine head fashion figure and it gives a few simple drawing lessons in making fashion figures. Oh yes, in fashion the sketch is called a croquis --pronounced "croaky" like the frog noise.
http://www.fashion-templates.com/about/creatingfigures