Clogged duct?

I went on an overnight business trip and had to go 6-7 hrs without pumping, 3 times in a row. My baby is 4 months and eats at least every 2.5 hours. Well, got home from the trip Thursday night and she's been draining me pretty good since then. Now, Sunday night, half my boob is hard! And she can't get any more milk out. Pretty sure it's a clogged duct, but would it be related to the trip, 3 days later? It doesn't hurt yet but I'm terrified of mastitis! Nothing is coming out pumping, nursing or hand expression. I just noticed it like an hour ago. 😭any ideas?