Hi guys  I have a condition call phimosis but mine is only when erect. As of recently me and my gf have been trying to have sex but unable to do it since she says she is too tight and another reason is i feel pain whenever intercourse takes place. We can go up and down a few times before i lose erection due to the immense pain. We tried to had sex 3 times but out of the 3 times only 1 time i manage to fully penetrate her but tearing appeared on my penis. I'm considering to do the following:
1) Z-plasty
2) Lube
3) Circumcision if really needed.

This is my first time having sex but not her first time. Hence my predicament. Is there any other way i can do to make it better? Any advice will be good. I have been asking around my friends but no answer from them.

Thank You.