baby hasn’t pooped in 3 days

Mystic_Gemini • single mother by choice to an amazing little boy - 12/22/17

We usually get 1-2 dirty diapers a day. Had one Thursday evening but not since (it’s Sunday morning). Still getting 6-8 wet diapers a day and he doesn’t seem uncomfortable. He’s eating normally. Mostly breastfed but he does get a little formula at the sitter’s during the week.

When should I worry?

Edit: I should have said, he’s 15 weeks old.