I second Hope's post.
I am in my 40's too and only had minor constipation through out my life. A couple of bad BM's and fissure hell. I am now 4 wks. post LIS and hopeful again.
The miralax has been a godsend for many of us; you just have to figure out when to take it and how much. I was taking it in the AM and was still having firm BMs so I switched to after dinner and that helped me.
I was worried about all the things you are too. I worried and worried from the moment I woke up til I went to bed, but I had to let it go and focus on healing. Keep reading posts on thi site and you will see that you are not alone.
I don't want to be on miralax forever but I am sticking with it til I am healed and then I will worry about weaning off of it.
I did get some adivan (some people get valium or Xanax or anti depressants) from my doctor to calm me down when I was in major anxiety mode. I was going through a rough patch and hypervenilating, dry heaving, sobbing, etc. I realized the anxiety and stress were hurting my healing process almost as much as the firm BMs.
There IS a cure but there is a lot of experimenting and changing of diet before you find what helps. It IS very frustrating and depressing but don't give up.
I have a friend who is vegan and eats super healthy and she is chronically constipated. My boyfriend is a somewhat poor eater and he poos everyday sometimes twice a day. She worries constantly...he worries about almost nothing. Is there a correlation? I don't know, but everyone is different and you might make a few missteps along the way (I did), but trust that you will get better someday.
Take care Alpha.