The mucous DD has in her nappy looks like large boogers, larger than pea size. It sticks together and does not take on the form of the nappy, like her regular poops do. More ball like, KWIM?
If you suspect it, why not just eliminate all obvious sources of milk, Liz? Might not be MPI, but many babies struggle with dairy overload in mom's diet in the first 3 months, and might just be that you need to curb the intake.
As you know I cut out milk from the start, had a few slip ups and paid dearly for it. But really, not having her cry for 2 hours at a time - except the bedtime cry is still there

- each time in her A time makes up for not being able to have dairy and MANY other food groups.
BTW, DD started off with exceptionally watery poops, would squirt about a foot far if she did not have a nappy on.