First of all, I'm jealous that you're 17w and your pre preggo pants are just now starting to feel tight. Mine got tight around 12 weeks.
I tried the BeBand from Target ($16?) but didn't care for it, I felt like you could still see the unfastened part of the pants through the band to tell that I was wearing unfastened pants with a band over it. I just retired my last pair of pre preggo pants this week and went straight to maternity pants instead. Belly bands are so cheap it's worth a try to see if you like it, though.
To the PP who said it smooshes your pants into your body, have you tried putting on the band, then pants over it, then folding the top over the outside of your pants?