I look gross in every outfit I try on

Women especially are their own worst critics. You would need to be severely beaten with the proverbial ugly stick to look gross. You are very pretty. On those days where nothing suits you, just get back to the simple basics. A pair of shorts (khakis for example) and a pull over. T shirt or polo, it doesn't matter. Then some sandals. You are done and you will look perfectly fine. Simple and easy, no stress.