Originally Answered: Baby has constipation and a bad diaper rash Any suggestion on what to do?
It seems like you are doing all the right things. I noticed a couple of things that you may not have tried. At this age I was giving my daughter the smallest bit of Miralax in with her water, the results weren't immediate. I was advised to give it to her after I kept complaining to the dr. who eventually had us take her for a barium enema. I would have loved to try the Miralax 1st, but apparently there are potentially urgent issues surrounding constipated babies. So, please make sure you check with them if this continues. However, I really think that a suppository would have worked if the baby really had to go.
For the diaper rash, do frequent soaks in a small bath with some baking soda. I did 4-5 times when things got really bad. I used plain old zinc oxide, instead of desitin. It was less oily and easier to wipe off. I also found that baby wipes exacerbated the problem. Try using plain old cotton balls and water (keep a water bottle available at the changing table).