I'm worried I look incompetent at work, what can I do?

Reflect on why you feel incompetent. But first look on the positive. What do you know about your job? Why did you get that job. You convinced someone to get that job. So what makes you unsure? Can you look something up? Refresh some knowledge to give yourself more theoretical competence. And maybe something practical. Dress in something you're feeling well. It doesn't have to be obvious. Your favourite underwear, lucky socks, a neclace? Something to start your day in a good mood. :)

You might have the Fraud Syndrom : a trend to feel incompetent or not deserving you seat on the table. Try remembering everything you've acomplished until now and keep in mind you know your stuff.

Do you have a manager or mentor you can talk to? I’ve found that our colleagues and supervisors can make great teachers and are often more than willing to help train, educate, and develop skills and confidence.

Ask your manager/colleagues to give you advice on your work. By doing just that, you are showing interest to work harder and it can help you improve.

Confidence should come from within. Find out things you are good at, and accept things you could improve. Everyone is good at something :)

Have a chat with your immediate supervisor. Try to understand your progress from his view and ask for a feedback. Also lay out what you want to achieve and have a long term goal. Take small steps and have personal achievements. It can be learning a new skill which may help you do your work more efficiently. Also learn from others on the team who consistently perform well. And lastly don't be afraid to ask for help and you will see a great deal of change on the horizon.

Ask your supervisor or a co worker for help and their input. It may just be you worrying and you’re actually pretty competent.

It often helps to talk to your employer about it. Are there areas of your work you feel you need help with? If so, explain the areas you feel you are weakest and ask them if they can help? A company I once worked for paid for me to go on a course to improve my skillset.

Work diligently and update your coworkers on your progress and your troubles. Don't compare for now, focus on what you can do.

Once you have more confidence in the things that you do, you’ll do better. While you are doing things, tel yourself you can do it, grow confidence, and you’ll feel better about the things you do.