Every time i clean my belly button every other shower it hurts?

It hurts for hours usually 10-15 hours straight it throbs and is a sharp pain. I've had this since I was born I guess. I remember as a kid I'd have the problem too and I only cleaned it 1/3 showers/baths.

I told doctors over the years and they just say they don't know and that if I had it for years it's probably nothing but it's severe shooting pain for 10-15 hours and I'm so tired of it. It feels like someone is stabbing my belly button with a knife it's that intense.

One thing is my belly button is shaped weird. It's not a typical oval it's a slit like this ->

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Just a line it's always been that way even as a kid. I'm not sure what this pain is. Any ideas? I tried googling it says infection but I've had it since I was born.. Thanks