What does your character really,
really want to do? Have you talked to him about it? Does he feel you're too restricting and you're not letting him be himself? Does he think that the plot you've given him isn't the one which lights his fire? If so, what would he do differently?
Sometimes characters can really come alive if you sit them down at your kitchen table (or wherever it is you chat to your friends & family), make him a cup of coffee (or does he actually prefer beer? If so, which brand?) and ask him (a) what one thing does he want to achieve in the next 3 months? (b) what one major past event does he regret?, and (c) who does he hate most of all and why?
Jot down his answers and weave them in. And Emma & Kate are right in that everyone goes through a bad novel patch during each novel - you have to know when yours will come (mine come at 30,000 & 60,000, regular as ruddy clockwork) and work round them. When I get to that point, I put my character in a sex scene. It may not get into the end product (but hey it usually does ...) but hell it cheers me up!
Go for it!

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