Congratulations! That's an awesome feeling, isn't it.

If I were you I'd keep it. Most of my large clothes got tossed or donated. I'm glad that I hung onto a few that I wore when I was at my largest, though. I kept one XXXXL shirt and two pairs of pants (slacks & jeans size 56). They make a great visual in reminding myself and showing others just how far I've come. They are also a warning; a reminder of a place that I never want to visit again.