How Come Line Breaks Don't Work Right for me?

Ever since I’ve been posting on this forum, if I hit enter to skip to a new paragraph it doesn’t hold. Once I hit post, all my paragraphs run together and I have to edit each post to separate them. Is there something I’m doing wrong or is there some setting I need to change? I’ve never had this problem on any other forum. Bitcointalk works fine for me too.

Example 1:
This sentence will
run into the one below it

Example 2:

This sentence won’t

run into the one below it.