I feel like a sinner, then I feel like I am a fun guy, then I feel like a loser, then I feel like a good Witness, then I feel like a bad Witness, then after a good workout I feel like chasing girls, then I feel bad again.
It's an endless cycle. After spending hundreds of hours in Watchtower indoctrination sessions (meetings) you really can't be expected to act any other way. The Watchtower does a great job of making the lives of their members confusing and stressful. That's what I experienced in the JWs as well as many others.
I suggest you read Crisis of Conscience. Not only is it one of the first stepping stones people take in leaving the group, but it is an excellent tool to help cope with being a JW, especially with the situation you are in.