I can't really help in this side of toribash but as a person also with this problem. It isn't with "you can't draw" it's usually because you're using a mouse. Don't know if its just me but try this. Draw it on paper then scan it in a printer, use this as a base and begin using that as a guide. It's really hard to freehand with a mouse. If you really want to make this a full-time thing or something you'd use a lot then you can also invest in a graphics tablet
http://www.amazon.co.uk/s/ref=nb_sb_...raphics+tablet here's a list I managed to find in 2-5 seconds on amazon, Good luck !