My poop has been really soft for the past week?!

Ok so ever since i was 3 years old my poop has always been really hard and gigantic, and it would always hurt to go, until about 1 month ago when i took a medicine called miralax, for 1 night, and then ever since i have been going every day. But last week my stomach started to hurt during school, and when i got home, i had diarrhea/really soft poop. the same thing has been happening for the the whole week. Its not exactly diarrhea but its really soft. I still go every day. Also i have been taking Vyvance for paying attention for the past 3 weeks, and i didnt have problems until now, also the other day i took melatonin to help me sleep to. Im worried, about this, is there something wrong with me?