Switch from uverse to DirectTVNow

I very much miss being able to stream to my PC/Laptop. If I switch from uverse to direct tv now (or whatever it's called these days) and keep my AT&T internet 100, will I have to pay additional for unlimited data?  My fear is that once we begin streaming TV we will quickly go over the limit. We have a TV on in our house pretty much 18 to 20 hours a day.