I think the issue lies within what it is you’re actually insecure about.
It’s definitely hard but it’s one of those things where it might be uncomfortable at first showing him but, after a few times of doing so, you’ll feel more confident gradually.
If there’s one thing I would say it will be to look at things from a different perspective and understand that we all have flaws; it’s a part of life. Learn to love your flaws because that is what makes you unique.
They say that you should love yourself before loving others and there is some truth to it.
I would say to talk to him about what it is you’re concerned of, and honestly, I doubt it even matters as much as you’re making it out to be.
Don’t forget that it is only you and your thoughts getting to you; remember that being in an intimate relationship, your body is more likely going to be appreciated than critiqued.