ok so I've drawn a 2d sketch, I then try to end sketch and "Can not rebuild the feature using this sketch". I choose the show the problem using check sketch option. It then says the sketch has no contour geometry to try to fix.. press ok. So I click ok. Default gaps smaller then setting is 0.0241069 and there's no problems found. I raise this to 800mm and 1 problem alerts "a small entity". A line is circled in yellow in the centre of it. i zoom in all the way and there are no breaks in the line and it is joined at the ends properly. I don't know what to do!!! I'm teaching myself how to use solid works and it's very frustrating! I've tried redrawing it, opening new sheets, restarting it.. nothing! Also I can't get a circle to snap properly to a line. Even drawing a simple circle then drawing a line to end on the circle it snaps on but when I zoom in it's actually not toucing or its over lappin. If I then try to trim it the whole line disappears. Please I've literally spent hours trying to fix this.
I understand your frustration. However, after you use SolidWorks for awhile, it will become easier.
Your pictures do not show the whole sketch or what type of feature you are trying to create. Please upload model you are working on errors and all.