The proper way to add space is through css. you could add do this for example:
<p style="margin-top: 6ex;">This line will have space above equal in height to 6 letter x's.</p>
even better would be to create a style in your css file that does that, and then you just tag your line appropriately with a class attribute. for example, if you did:
<p class="biggapper">This line will have a gap before it shows up/</p>
And then added to your css file:
.biggapper { margin-top: 6ex; }
you would be doing your gap ala modern standards. The real benefit to this is you can changet he gap in the future for every occasion of biggapper in your html merely by changing the css value ONCE.
We’re supposed to separate style from content these days.
But if you really insist on putting in multiple breaks, you can create a functions.php file in your theme, and add code that will disable the automatic removal of them. If you search this forum for wpautop, you’ll find a thread where it’s explained how. You will also likely need to disable the visual editor for your account, and click off that option for fixing xhtml nesting (I forget what it’s called, I think it’s under writing options).