Not sure where to go for speaking ability

I’m not sure if anyone else has this problem, but over the years my listening ability has drastically surpassed my ability to speak. I can understand most words even when spoken at a native speed, but where I tend to struggle is speaking.

Specifically, I know what I want to say, but I often fail to put it in a way that sounds natural. Here’s an oversimplifies example:

If I were sick, the first thing that comes to mind would be 病気があります。

But this isn’t what most Japanese people would say isn’t it? Just a simple 病気です。

I’ve exposed myself to a lot of listening practice: podcasts, television shows, etc. but idk what I’m missing to cause such a disconnect between what I hear and what I want to say that causes me to stumble over words.

Thanks