Help please. when i ejaculate i hold my penis so nothing come out. is that bad?

Please don't do that: You probably won't damage your body, but it hurts, you'll find it emotionally frustrating, and what's the point? If this is how you're practicing birth control, it's going to fail -- nobody's got this self-control. If this is a "spiritual" practice, please talk with somebody sensible -- maybe even dad. Embrace being a man, and all the joys and responsibilities that go with it.