Thanks for your query.Based on the facts that you have posted it appears that you have
which got injured during sex and has not healed up completely.
You are getting it injured repeatedly during sex.
Most likely this is due to a band of adhesion
between frenulum and glans penis
Please consult qualified Urologist
for clinical assessment,if needed you may to get that band excised under local anaesthesia.
It is a simple surgery and will solve your problem for for ever.