Need help with my vision problems?

I wear glasses for medium myopia and astigmatism. Without glasses my eyes cross terribly when I try to see up close and I get double vision. With them, I feel strain when seeing up close but the eyes don't cross as much even though sometimes it feels like they might. At my last exam, they noticed something called exophoria (I think) and started talking about prism glasses. However, the doctor said that prism only gets worse (your eyes need more of it) so she didn't give it to me. Do I need reading glasses? Are my distance glasses too powerful? I'm only in my 20s and don't want to go cross eyed. Thanks for the answer! I do have myopia. I am nearsighted. And yes, one of my eyes move outwards. I still get double vision when I'm reading without glasses.