How does anyone get above zero points when you lose 20 points on every loss?

Solution 1:

It depends on who you're beating and who you're losing to. You get more points for beating someone with more points than you, and you lose more points for losing to people with fewer points than you.

That being said, if you're getting about 8 points per win, you're beating people about on par with your skill level or slightly worse. If you're losing 20 points with your current low point total, it's because you're losing to people with a very low rating.

In order to advance in points you have to start winning games against more difficult opponents. In short, you must improve your own game.

Solution 2:

Through learning some new information, I have found out why you are experiencing this.

"In particular, Blizzard said that their solution to the Bronze Zero phenomenon (where players whose MMR is below Bronze Zero win only 2-4 points for a win but lose 20+ points for a loss, thereby anchoring them to 0 points) was to place those affected players in new divisions."

In other words, your match making rating (MMR) fell below the Bronze Zero cutoff, which essentially doomed you to stay at 0 points. There are actually rankings of divisions within leagues, and thus Blizzard plans to move people experiencing this to new divisions with high modifiers to fix this issue. Thus, other people manage to earn points because they have not fallen below that threshold, and thus are not trapped by the bug in blizzard's match-making code. For more on division rankings see this thread.

Specific quote is from this post. That poster is essentially the leading source of information on how the ladder system works in SC2 outside of blizzard itself.