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If he never harmed you as a child, it's probably accidental but if it makes you uncomfortable, it's simple to tell him that. If he loves and cares about you, he won't be offended.
Dr. Z isn't available on the site so the question went to me.
If it feels inappropriate to you, it's best to say something simple as I outlined above. That type of statement works well whether it was accidental or intentional. If you find yourself worrying about it, it's best to set a clear boundary. Something simple without making a big deal out of it. But letting him know that it makes you uncomfortable. Be sure to add an I love you Dad in there too, if you do love him. And smile. I think you'll feel better overall if he didn't touch you in places that made you wonder.
The only way I can think of to figure this out is to mention it to him as I outlined above. If it was intentional and inappropriate, he will absolutely stop doing it. If it was accidental, he may become more aware and conscious about it and it will decrease but there may still be times it happens accidentally. So the only way to tell, is to say something to him. Remember that if it's intentional, it's important that you say something so it stops. If it was an accident, he will become more aware because he loves you and will understand.
I hope this helps.
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