Sex- Painful or pleasurable??

I've had sex like 4 times now. And I'm getting there with finally fitting him. But for some reason when we have sex, it is a little bit pleasurable but not like they say it is meant to be like. It is still a bit painful when he puts it in and when he goes too deep, but I don't know how to make it pleasurable for myself. 
Apparently You need to "activate your G-spot" to have more pleasure but I can't seem to figure it out?? 
Is it going to be like this for the rest of my life?? 
What can I do? 
Help me please!!