What does your current routine look like? Sometimes it's best to keep it simple and just hit them heavy. Stay in the 6-10 rep range with exercises that allow you to move the most weight. I personally use a combinaion of straight bar curls, heavy preachers and seated dbell curls or variations of these three movements. Sometimes I may do cable curls with the straight bar attachment and really emphasize the negative on each rep. I may do one arm preachers with a dbell or I may change from regular seated curls to incline dbell curls. Either way, I stay within those three basic movements. That's what works for me.
Also, you probably have achieved a good level of growth, but your'e just being a little hard on yourself. We all do it, it's just the competitor in us. Just be careful what standard you're comparing yourself to. If I constantly looked at Ronnie Colemans back and compared his to mine, I would consistently feel like a failure! Just my two cents!
