It sounds as of you are concentrating on penetrative sex, but sex isn't just about penetration. You can pleasure each other with oral stimulation, use sex toys, massage and other things that increase intimacy. For women penetrative sex is not always the total path to orgasm. It depends on the position - for example, clitoral stimulation is less in some positions than others.
You might find it helpful to experiment with pleasuring yourself to achieve orgasm (if you haven't tried this before) in some alone time, so that you are better able to direct your partner about what feels good and how to help you to have a pleasurable and less painful experience. While it is nice that you are taking his needs into account, it should be reciprocal and he should be wanting to work with you to make the experience jointly pleasant.
Some women have found that where hurts depends on where there endo is located - so some positions suit better than others and are a lot less painful.