Confusion in buying the game

Hey. So i finally decided to give ESO a try but am bit confused. I already have the base game + Morrowind from some time ago but i only played for idk 50 min. But as i´ve been replaying oblivion and skyrim i finally decided to completly go through ESO (for the story).

So back to the point. As i am a steam user i have the game there but when i wanted do buy the rest of the chapters (in the package with the new chapter coming in June) Steam kinda rejected me:

According to our records, you already own one or more of the items included in your cart.

If purchasing for yourself, you will not receive an extra copy of:

• The Elder Scrolls® Online

Would you still like to continue with your purchase?

So my question is, will i normally get all the chapters? or will I lose my money? Or is there any other way how to get other chapters and kinda not lose money since i already have the first two chapters? (of course i know about the way of buying it one buy one, but that is hella expansive)

Thanks for your replies