You need to get circumcised.
Thanks for your query,based on the facts that you have posted it appears that you have Phimosis
The white substance that is getting collected beneath the foreskin is dried secretion of the glans penis
Please consult qualified General Surgeon
for clinical examination to confirm the diagnosis.
You need to get circumcised .This is a simple surgery done under local anaesthesia as a out patient procedure and offers permanent cure.
Hope I have answered your query ,please feel free to ask if you have more questions ,
I shall be happy to help you
Thanks and Regards.