Why does my penis go on erect for no reason?

I have the ability to be resting somewhere and for no reason my penis goes on erect. Is there something wrong with me? I'm 18 years old soon going to be 19. Is it growing are something? By the way is 8.0 inches too large for a penis. My ex say it is too large and she think it will injured. Is it going to grow any more?

Please help I’m having a plethora of issues here….

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Answer:
nothing is wrong because it happens to me…it sucks though because sometimes it can happen at the wrong places and we need to hope no one tells us to get up or move.

it is quite normal but when it happens to me…I just think about whatever comes into my mind…don't get nervous cause that can make it worse…it's like a cold, you should let it run it's course…if you relax it should go down within 2-3 minutes

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Answer:
when you relax it is normall to get an erect! and you are penis is normall

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no issues there buddy, its all working properly.

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Answer:
LIAR.

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He's lonely or just bored. Play with him…

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It's a natural thing don't bother so much.

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8″? you’re living in a dream world.

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your a healthy male. But 8″ really get a life

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well mabe your body is just making sure its still working and 8'' is not to massive

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This happens to everyone. and 8 inch is bigger then average, but its ok lol

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Answer:
thats normal size and your a teenager thats y u get hard ons for no reason!!