Sweatshirt Salesman

I really love my ENT, but I was confused by this today:

Doc: How's your job?

Me: I love it - I have a deadline coming up, so I'm busy selling to make goal.

Doc: I guess that means I need to buy another sweatshirt!

I don't... sell sweatshirts? I wonder what he thinks my job is? A sweatshirt salesman?