Seriously Constipated...please advise

So I figured out what is causing my depression, anxiety, and brain fog...It's my gut.

I went to the hospital today because I couldn't take the pain anymore. I didn't put much thought into it but for the past 2 months I haven't really had any bowel movements. Today my body told me enough was enough and I needed to do something about it.

At the hospital they took an xray and saw that I am full of poop. I saw the xray and was in shock, I mean I am stuffed full of it.

A couple of days ago I ordered Oxypowder , but I am still waiting for it to come in the mail.

The doctor at the hospital prescribed me Miralax.

Would it be safe to take this in the meantime until my Oxypowder gets here? Also would the 60 tablets I purchased of Oxypowder be enough? Is oxy powder strong enough to break me loose from this constipation? Thanks.