Pain during penetration

Hi there!
I have an issue with experiencing a fair bit of pain when my SO enters me. We use lube and although it helps, the pain does tend to linger just a little bit during sex. After sex I then get a sore uncomfortable feeling down there, kind of similar to chaffing. In the past the pain has been bad enough that I've had to stop the sex completely.
Does anyone else have this issue? Or does anyone know how to relieve the pain more?
Thanks!