I have been peeing every 20 min. for the past two days now. what could this mean ? all i've been peeing is water

Different thing: Frequent urination could be from various conditions including urinary tract infection, diabetes (mellitus or incipidus), other infection or side-effect of medications. I suggest seeing a doctor for a urinalysis if it does not resolve in a couple of days for evaluation.

Diabetes?: If you're urinating and drinking a lot it could mean you have diabetes mellitus or another more rare condition called diabetes insipidus. A UTI can also cause frequent urination. I suggest that you see your doctor to help you figure out if you have any of these issues.