The biggest problem is likely not just placement, but mismatch: your lights appear to have different brightness and color temperatures. For a simple three-point setup, start with three similar bulbs/lights so the light matches more naturally.

A practical low-budget approach is:

• use 3 inexpensive bare-bulb/workshop lights
• fit them with similar bulbs, ideally the same type/color temperature
• soften them with white fabric or bedsheets used as diffusion
• place them on simple stands so you can position them consistently

Bedsheets can work as diffusers, yes. Just keep heat and safety in mind, especially with hotter lamps.

Typical arrangement:

• key light: off to one side of the camera, slightly above eye level
• fill light: on the opposite side, dimmer or more diffused
• back light: behind you, aimed to separate you from the background

Also, don’t focus only on wattage. What matters more is matched bulbs, light output, and controllable positioning. If you keep your current mixed lights, you may keep fighting odd color and balance issues. Matching all three sources will usually improve the look more than any clever placement trick.