I have a small dick/penis. around 3.5 inches when erect. is it normal?

Yes: Penis size doesn't matter to most women, but it seems to be an important topic of concern among many insecure men, and it makes a lot of money for people selling useless garbage on the internet who take advantage of those insecurities. Be happy with what you have, it's better than half the population that doesn't have one at all.

That's plenty: This is all you need, tough smaller than average. Stop comparing yourself with the guys in the dirty pictures online. I trust you have other areas in which you can excel, and this is actually a mixed blessing. It gets harder, you won't have compatibility problems with some women, you can stimulate her best nerve endings in the front more easily, and getting oral sex will be better.