Few suggestions for you
Thanks for using healthcare magic. I, Dr Abhishek Kapoor, would try to help you in this problem.
I think, in your case due to size, you may feel pain due to which you face problem while intercourse.
Just some suggestions:
1. long foreplay and lubrication is certainly a good idea, then maybe you could try to get penetrate vagina before he has a full and hard erection, maybe if he insert his penis into your vagina while he is having something like "half-erection", it can be less painful and then when the erection gets stronger inside you, the vagina can adjust to it more easily.
2. Try to experiment with different positions, especially such positions which allow you to have control over the regulation of penetration, its depth etc...e.g. if you are on the top, it can make you less worried about pain and in case of pain you can probably find less painful way.
3. Last but not least, you can try to focus on non-penetrative sexual activities (oral, manual...) as much as possible - in order to have more pleasurable feelings than pain which has been a result of penetration... Hopefully you will not avoid sex because of fear of pain, it would be helpful if you could enjoy at least non-coital sexual contacts during this period.
I think, you would feel satisfied with answer. In case, you need more suggestions, you can consult me.
Dr. Abhishek Kapoor