Can I use miralax during pregnancy (PLEASE HELP ASAP

So during my first pregnancy at the end I was so constipated I wouldn’t go for weeks so they recommended miralax . I used it almost everyday. I’m now 9 weeks and super constiptaed and my appt isn’t until Monday and I still haven’t been seen. I can’t wait until Monday I’m wondering if it’s safe this early in pregnancy to use miralax