Hi, It appears to me that you are an unmarried person. Are you? If yes, ejaculating on just thinking of sex is normal. You dont have to be upset about it. It wont be there once you are married.
Yes you ejaculate faster when you watch porn.
The looseness you describe in your penis is also not a disorder. After ejaculation everybody's penis becomes flaccid (loose).
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If you have more questions or concerns, please contact privately over phone. I will be happy to clarify all your concerns.