Looking through the history of your posts which is available to anyone on the profile page I see:
1. Some posts were flagged and others were not. So the posts vary quality.
2. Among the flagged posts, some were probably flagged as 'duplicate'. For example the post about Google Spanner. The duplicate mechanism is subtle. While the ArsTechnica story was not popular, the news about Google Spanner was and there was a very substantial news discussion.
3. Some of the flagged posts appear to be what some users would consider low quality by Hacker News standards. In those situations, users often flag the content.
4. It is possible but not certain, that some of the posts came from sites that have such a high probability of containing low quality content that any link from those sites is killed just for the sake of reducing noise. Turning on 'Show Dead' in your profile and going to the |new| page will allow you to see that this is not uncommon.
Finally, it can often take some time to gain intuition about what does and does not make a good story on Hacker News. It usually takes even longer to gain a feeling for what makes a good HN comment.
My advice is simply to find better stories because that's what everyone has to do.
Good luck.