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I am worried you may not be taking enough care of yourself. If I say, 'I am hung up on how much you take care of yourself', is it right?
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hung up on (something): to be extremely interested in or worried by a particular subject and spend an unreasonably large amount of time thinking about it (Cambridge Dictionary)

BulbulTadaI am hung up on how much you take care of yourself.

It's correct, but in my opinion it's a bit extreme as a way of saying you're worried. Besides, it's slang, and that takes away from the seriousness of the topic. The following seem better to my ear.

I'm (very) worried about how much ...
I'm (very) concerned about how much ...
I'm (very) troubled about how much ...

Also, I think the worry is really about how much "you" are not taking care of "yourself". Possibly

I'm concerned about how much you [are / seem to be] neglecting to take care of yourself.

You can soften it by saying seem to be instead of are.

CJ

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CalifJimI think the worry is really about how much "you" are not taking care of "yourself".

I know 'you' used to neglect your health, and now I am troubled to think you may still be neglecting your health. More probably there is neglect to say you are/seem to be neglecting. Should I say?

I'm concerned/worried/troubled how much you are likely neglecting to take care/not taking care of yourself.

I didn't know it was slang.

CalifJim I think the worry is really about how much "you" are not taking care of "yourself".

Yes. I am disturbed/concerned/troubled/worried about how much 'you' are likely neglecting your health as you used to do. Otherwise it would be you are/seem to be. Thanks.