Does anyone have any advice?

This is my second poll like this on here, sorry, but I'm just so stressed and scared right now. I turn 18 in a couple months and want to move out to escape my verbally and mentally abusive stepmother, but honestly, my body doesn't feel healthy. I keep getting pain in my chest, and I don't know if it's from stress or something wrong with my body or what. My stepmother always brushes off my medical issues I tell her about, and hasn't taken me for a check up in many years, so I have no clue what's going on with me but I know I don't feel healthy but I don't think there's anything I can do about it right now. And I'm worried about how I'm going to be able to pay medical bills in the future. Does anyone have any advice? I'm sorry, I'm just terrified and I don't know what to do.