Scared about my weight 😢😢😢

I'm size 24 and last time I flew I was considerably smaller, but I was still kinda almost uncomfortable. I sat in a chair yesterday and I was surprised how painfully small it was. I'm flying in 6 days, and I've been looking forward to this trip for months. However Im scared I may not fit in the plane chair and I'll get kicked off because I can't afford to buy a second seat 😢 I didn't really think about this until now. I have really thick thighs and that's what I'm mostly worried about. Has anyone had this problem?!