You have to stick with what you’re comfortable with. As you wear more, you gain confidence, but don’t push yourself. It only take one bad experience to cause anxiety. As far as having your under garments not visible, it’s more about what you wear over them. Loose fitting, darker shirts tend to show bra straps less. Panties are not usually a problem, loose fitting pants will help. Low cut panties like bikinis or hip huggers are less likely to show above the waist of your pants. Keep in mind, most often someone would really have to be looking to notice. Most people are just not that observant. We are our own worst critics when it comes to this. Find the styles you like and wear them with confidence.