Hey there
As for your second question, I don't think it will be a problem to wear a top and shorts for your doctors appointment unless you would have to strip.
Also doctors have seen a lot. They won't mind. It can be really scary, to let a doctor see those scars, but they won't make a big deal out of it. Especially if they are old. If they are new they might ask, but most doctors are really sensible about the this. So it'll be alright.
And if your scared your mom might see when you are at the doctors you could always ask tell her, that you want to go in alone. Most parents respect that.
As for covering up. Sadly there's not much you can do. I tried different kind of things to get scars to fade, even scar oil can only do so much.
You best bet is to keep them moisturized, for which aloe vera or cacao butter will be enough. It works better if you massage the lotion into the scars. It keeps them from raising when they heal (at least thats what I've heard)