drawing with a mouse takes more practice than it would with a tablet, its a different action.
using the pen tool is pretty easy though, i used to use it for all my textures befor i got my tablet.
your problem isnt so much a mouse problem, rather a design problem. dont worry about effects and stuff, work on design and mapping to start with.
its not just making random shapes and hoping it makes something, design something.
keep practicing and you'll improve. simple as that.