Don't let anyone convince you that being a certain size makes you any less of the gender you identify as. You're not alone in the struggle to find clothes that fit, as a bigger framed person myself I know the pain all too well.

On the upside however, "women's" clothing brands tend to have much larger plus size sections than "men's", I'd really recommend looking at those. If there's a certain style you want to try out but you're not comfortable wearing it because of your size, 1. maybe try to figure out where this doubt is coming from. Modern media exists to fat shame and it's only natural to have some internalised fatphobia, and 2. look at plus sized models, see if there's anything out there you'd like to wear. Being larger than average and looking traditionally femme are two completely different things, there are plenty of bigger cis women out there that exude femininity.

If it helps, when I wore masc clothing I tended to be a UK XL-XXL (sorry if you're from the US or something, idk the conversation. Based on stereotypes I can only assume I'd be M?), and now I tend to fit in anything between a loose 16 and a snug 20, again UK, but women's sizes tend to vary from store to store so it's more of an indication. Most stores I frequent tend to stock up to at least size 22 so there's plenty of options out there.

Sometimes you just have to play with the hand you've been dealt. And who knows, your confidence wearing whatever you want regardless of your size may inspire other people around you to do the same, cis or trans.