Why has my foreskin shrunk it always splits in a few places whilst having sex?

? BXO. You mayv developedbalanitis xerotica obliterans. This is a sort of degenerative condition of the foreskin which results in scarring or fifrosis of the opening of the foreskin. The only remedy for this is circumcision. Other causes are a foreskin that has never loosened up and now just splits during sex. Suggest you see a urologist.
Phimosis. Phimosis can occur at any age but as it worsens the thickening of the skin and further scarring can occur. Sometimes it will remain stable but more often than not, circumcision is required to correct the problem. You should talk to your physician or see a urologist.