Plus Size Maternity Support

I’m currently 18 weeks with twins and having really bad back pain to where even laying down hurts. Im looking in to getting a support band or belt. Does anyone have any good recommendations for something that with flatter me and fit right? Im usually a size 3x-4x in shirts. I’m just worried about nothing fitting and/or it making me look big because I’m not really showing yet I just look like I’m gaining weight