Welcome to e health forum.
In case, you are able to ejaculate during masturbation, then in that case, there should be no major medical issue with you.
Reducing the frequency of masturbation, should resolve your problem.
In case, you are not able to ejaculate even during masturbation, then it could be due to the technique of masturbation, you follow.
In such a situation, consulting your doctor or a sexologist for a proper examination and proper treatment should be helpful.
I hope this helps.