Don't worry about the size and work on your technique. Read about penis size here:
https://lovematters.in/en/resource/penis-shapes-and-sizes
https://lovematters.in/en/news/penis-top-five-facts
https://lovematters.in/en/news/worried-your-penis-too-small
https://lovematters.in/en/news/what-women-penis
As for painful sex, yes, sex with a big penis can be painful.
https://lovematters.in/en/news/top-tips-vaginal-sex-big-penis
https://lovematters.in/en/news/huge-penis-painful-sex-whats-way-out
If you would like to join in on a further discussion on this topic, join our discussion board, ‘Just Ask’
https://lovematters.in/en/forum
Don't worry about the size…