Read and understood the problems you and your boyfriend are having after sex.
It appears that it was lengthy and strenuous for your boyfriend causing him pain in abdomen as a muscle strain.
And you have burning for the same reason.
Simply take rest, use proper lubrication wherever necessary and have a stop-gap sometimes.
Take care. Drink plenty water orally.
Wishing you a speedy recovery.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.