Juelqing 10 mins three times a week for 6 months might help. One day off inbetween. Also, stretching the penis before juelquing.
Don't watch porn and compare yourself with the men there. Those guys don't have normal size penises. Average size in EU is 15.2 cm. Think about that for a moment.
There is no fun in having a bigger size penis when girls are hurting. There are girls who fantasize about big but when they're experiencing a guy pounding them it's not always fun.
The experience is not the same as the fantasy.
Also, having a big penis (or a regular size) and start anal pounding like you've seen in porn clips is not a smart way. The porn actresses warm up with buttpluggs an hour or two before the anal scenes. They also use a lot of lube.