When you first start writing articles, especially if you have not written much before or lately, it will be natural that your articles are not going to flow easily and naturally. That will change as you write more articles, especially if you are making an effort at reading a correcting your articles, and perhaps even having a friend or family member read them and take their suggestions.
Remember, if you ask a family member or friend to proof something for you, always be appreciative of their help, and do not let them know that you disagree with a comment they have made. You see, if they are afraid you will be defensive when they offer honest criticism, they will simply begin to withhold the honest criticism and simply tell you the article looks good. You do not want that. The more criticism, the better. You see, you can always choose to ignore the criticism, but if you do not receive it at all, you will not be able to improve your writing or make the necessary adjustments to become a better writer.
Another very useful technique for proofreading your own work is to read it out loud, word for word. You see, when you read it silently, you might tend to overlook some small words or prepositions that your brain simply scans over, but a fresh reader would pick them up immediately. By reading it aloud, you will catch many of your mistakes.
Take some time to read online articles by other writers, and make note of the ones you like. What are they doing differently than you are doing? Are they writing more or less, with stronger or weaker language, at a higher or lower level. If you are a scientist, for example, you may be used to communicating at a different level of vocabulary than the average person reading your articles, so you might need to make some adjustments to make your articles more readable.
If you are genuinely having a difficult time writing at any level at all, look into an online correspondence writing course.
But at the same time, do not allow your lack of writing ability stop you from writing articles. Write and publish at whatever skill level you currently possess, and you will get better over time. Do not allow the fear of not writing perfect articles stop you from making money online or developing a web business.