Hi Rob,
Sorry about your troubles.

It is too early to come to any conclusion and too early to begin worrying about it.
However, if you are concerned, you might begin keeping a log of your diet and noting any accidents, in case there is any cause-and-effect here.
Yes, constipation very definitely can cause fecal overflow. It is counterintuitive.

That is the nature of my bowel incontinence. The Miralax will not hurt and may help. Also watch your fibre intake and try to stay physically active.
Hardened fecal material forms and blocks the passage until a sufficient amount of soft or liquid stool backs up to flow around it. It overflows, usually in the form of diarrhea, followed by some solids [sorry for the TMI, but necessary]. Although it usually is perceived as diarrhea, it is caused by the constipation. Therefore one treats the constipation and not the diarrhea. I am chronically severely constipated and take two caps of Miralax per day, one in the morning and one in the evening.
--John