My scream is good but it is almost like a whisper, why? Its not nearly loud...

Because what your doing is only pushing air, this is when you just use your throat to get the noise out of you, which isn't hard and unfortunately is not considered screaming. you need to use your diaphragm to pull the air up and get the noise from right down from your gut and bring it up, as opposed to what you can feel when you push air which is only just from your throat.

you definitely wont sound the same when you initially start to actually scream but you need to give it time and practice before you will finally get those noises coming out from you that will sound the same.