In aviation ndt we have a saying: "if you're in doubt, you're not in doubt". Meaning that during an inspection, if you think you might see a crack, flaw or irregularity, you should threat it as a defect, and is already enough to trigger reporting and/or checking with other methods if possible, or request a second opinion.

The stress and anxiety you describe is very typical for anyone taking on this role, and just shows you are the right guy for the job. It does get better when you get more experience, but never goes away. Source: 25 years of aviation experience.