To answer your question: No, you cannot conduct a usability examination by yourself.
You have some options to improve your user experience, depending on the resources that you have available.
- You could conduct a heuristic evaluation, which will probably uncover some problems, but doesn't necessarily tell you whether users are able to complete workflows.
- If you have access to internal people who might be able to represent users, such as sales or field people, you could have them participate in a usability study. Any results from such a study are likely to be limited, since internal users are likely to know your product very well, or jargon that your product uses. This is probably an improvement over conducting a heuristic evaluation yourself, since at least you'll get the opinion of someone else.
- Talk to your marketing team to see if your company has customers who are already under NDA, and who thus could participate in a usability study (either local or remote). This is an improvement over having internal people, since these really are your users. However, they might already know a fair bit about your upcoming product, and so might be tainted and not give great results.
- Talk to your management and your legal team about what would be required to conduct research with real users. Non-disclosure agreements will protect your company's intellectual property. If you need assistance with this, most user research consultancies will be able to discuss with you what you will need to do to ensure that your intellectual property is protected, how to recruit users, and how to conduct the study such that you get results that are valid and actionable.
Personally, I've conducted hundreds of hours of user research on products that have not yet been released. My research has been on highly-sensitive products, the most important features in those products, and I've never had anything get leaked. With good recruiting, a NDA, and a reminder to participants that you're showing them something that hasn't been released and that they have signed a NDA, you're quite unlikely to have a problem with someone revealing something that they shouldn't.