You need to look at your audience retention, probably on a per video basis, so you can study the retention graph. If it drops early, it indicates that your audience is leaving early, possibly through boredom, maybe it takes you too long to get to the point of the video, maybe the video it'self doesn't reflect the thumbnail.
But also, you could be very new. We don't know how many videos you actually have, so what might feel like a problem might not even be a problem and is simply part of the journey of youtube.