Belly band/support: when did you start using it?

I'm 21 weeks and starting to get big (or at least feel it). I have arthritis in my low back due to being a gymnast for 10 years, and it is getting more and more painful every day. There are days I can't stand up straight due to my back pain. For anyone who has used some sort of belly/back support, when did you start using it? I just feel like 21 weeks is early to start that. Also, I work at a running store and wear a lot of tight fitting clothes, so is there one that looks pretty hidden under tight clothes? Thanks!! Here's my bump pic below for an idea of my size.