I have the same fears but, as hard as it is, there's no point in focusing on them because we'll never have an answer to what will happen. I used to keep myself awake at night thinking about being reincarnated as some poor workhouse soul, or as a slave who had to fight to the death, or simply in a time period where I didn't have any rights. I would cry to myself over not having the freedom that I have now, about how awful life was in other time periods, but eventually I had to just force myself to get over it because regardless of what happens after death, my consciousness in this life won't be aware of it.
If reincarnation is real then there could be a whole universe to reincarnate into, the universe is ever expanding and in our lifetimes we won't get an answer to what else is out there. Even amongst people who do believe in it there's no consensus on how it works but even if you did end up in a poorer time period it would be all that you knew, so you wouldn't be able to miss what you didn't have. You would just get on with your life, and then you would die, the same as we do now.