I had a very similar problem when i first got my burm. He was as stubborn as a damn mule when it came to eating. All i can recommend is try different sizes and give him time to adjust bc mine took a good month before it began a good feeding cycle. He will eventually eat. If i remember correctly i placed a small hopper mouse(which is pretty harmless)in his cage and simply checked periodically to make sure nothing went wrong and eventually he chomped down on it within about an hour or two. Just needed some privacy i guess. So just dont give up hope. Ur little guy will munch hehe.