Breaks get lost

First of all, I would like to apologise for this topic, I bet this has been covered a hundred times before, but I can’t find the solution when I search for it. Maybe I don’t know how to search or what to search for.

The problem is that very often, but not all of the time, published version of a post or page ignores my “
“. I don’t know the technical term “new line using Enter”, but if I use the HTML reference I think you get what I’m after. ?
I can write a text and press Enter, and I get a new line to write on. If I want a blank line between the text and let’s say a header for the next part of the text, I press Enter twice, then the header. It looks fine in the editor – I publish – and the extra Enter/
is gone. I make ten Enter/
between the text and the header… same thing. I enter the HTML part of the text editor and actually type
before the <h>-tag, no difference at all. It all looks fine in the editor, but when I publish/update, it gets lost.

I’ve had this problem for the past years. Am I doing something wrong? Am I missing something in the way I write posts and pages? Is it a bug in WordPress? I’ve been using lots of different themes, so it can’t be a theme problem. I’ve turned off all addons without any difference. I’ve been using Internet Explorer, Firefox and even Live Writer. Same thing.

What am I missing? Is it me that has a bug or is it WordPress?

Please help.

Thank you for your time.