Company wants to fire me because im on sickleave

Hello i need advice. I have some lingering health issues and the company im currently working at hinted that I might get fired because of my absence. Now this is the second time I have this issues I was already fired from my previous job for the same reason. In both cases it was the same health issue (still unresolved and undiagnosed) and I wasn't missing many days overall maybe one week altogether.

Since im alone and need to pay my bills this situation makes my life very difficult.

My question is what to do in this situation? Did anybody experience the same problem and could give me an advice? Thanks