What do you think of me faking a picture of my id card to change the date to make me 18 and joining cam4?
That depends. Why would you do fake your date of birth?
because I was just 3 months short to 18 years old.
So you were still a minor to use cam4. It's wrong to lie and access adult sites when you're still a minor.
It is okay. I used a fake signature to make myself look legit.
That doesn't make it better. Not only did you lie but you also broke the law by signing a contract. You could get in trouble for child pornography too.