You may be just a little congested if you've been sexually aroused without ejaculating. If you are congested it may be painful to ejaculate, so try this:

Very gently massage your testicles between your fingers for a few minutes. Then arouse yourself and try to dissipate the pleasure from your genital area into your whole body by massaging your pubic bone area and gradually moving up towards you navel and then on towards your sternum, gradually drawing the pleasurable sensations upwards through your whole body.

This will help relieve the congestion in the most enjoyable way without you spending yourself. Repeat daily for 15 to 30 minutes or for as long as you like and as often as you like.

Hope this helps.