I'll be finally having my PhD defense by the end of this month. I am so nervous about it. There are a couple of things that really bother me. First of all, my research is not perfect. I have never won any awards in conference and I only have two publications as of now. Furthermore, my supervisor has already received reports from examiners but she has remained silent about it. Thing that worries me the most is my sample size is small. This has been brought up so many times when I sent my papers for journal publication. Regardless, my papers were accepted for publications although reviewers were not happy with my sample size. For your information, my research caters on rare disease in my population and there were not many I could get during my sample collection which took place for about 2 years. However my supervisor assured me so many times that it won't be a problem if I could explain very well to the examiners.

What should I do while waiting for my PhD defense? I have re-read my thesis multiple times and practiced the presentation. However I don't know what I should expect during the defense

I haven't done mine yet, so others will probably offer better advice. But based on what you've said I would suggest two things. First, (and this is probably really hard or impossible), try not to worry, as that won't gain you anything (and I know when I am in your position in under a year's time I will think that is ridiculous advice as well). Second, I would write a list of the key issues that there were with my research (such as the one you have described) and bullet point what you will say as a robust defense (where appropriate) or very clear explanation as to why it was the case, what impact you think it had, how it could have been done differently etc.