Bread too Heavy

First thing that you are doing wrong is making us guess at what you have done.  Could you post your recipe and the steps you took to make the bread?  Pictures can be helpful to if you are able to post them.

 i don't mind guessing  so  maybe you are having the same problem i had . i was kneading in way to much flour after i mixed the dough  it made a dence dryer heavier dough . try to mix the dough then turn it out and knead it without using more  flour so your dough will be more wet then let it rest  and fold like in the videos it really helps  

 now when i get finished mixing the recipe i add no more flour at all  and my  sourdough turns out pretty good thanks to this forum and pablo ;) 

 also watch all the videos on  this forum  so you can see the way to knead without adding more flour   i hope this helps i'm new to sourdough too  good luck

 and i don't think your doing anything wrong , just learning like the rest of us   hehe:)