Havent had a bowel movement in 9 days.help?! PLEaSE.?

so, i have an eating disorder and am in recovery i dont think my body is used to this much food.. i have had bad constipation..about 12 days ago i went 4 days without having a bowel movement and took these laxatives under adult supervision might i add. and i went ALOT. but then after that i didnt go, and i thought oh well must be all cleaned out..then a week went by and i told my dad, yesterday he called my doctor and they put me on Miralax. and its supposed to take 1-3 days to work. my doctor put me on 1/2 of the cap full. its the 2nd day and i still am so constipated,i can feel my stool around my rectum its hard and its not coming out. the miralax is supposed to be a stool softener, but im just worried. should i take a little bit more.. or just wait it out and if tomorrow i dont go, tell my dad and he can call the doctor? idk.