37 Weeks pregnant & all of a sudden constipated, what would cause that?

Yes, as you approach full time, Baby is taking up so much space, digestion can really slow down. Are you drinking enough? especially with warmer weather now and being heavily pregnant, make sure you are having plenty to drink. Also, perhaps you have changed your diet slightly lately, plenty of fruit and veg should help keep you regular. If concerned mention it to your midwife/doctor, All the best xxxx