I think you are suffering from the same thing we all did on our first hibernation. When I first got my little guy in December, he was already mid hibernation, and I was SO tempted to dig him up. But this is very bad for them. Even if your guy is eating a little, let him sleep. If he is not coming out on his own, then so be it, but don't dig him up. This is terrible for their physical AND mental condition. He is woken up from what he planned on being a several month nap, so he feels very vulnerable as he is cold and cannot react to danger, so he goes to warm up. Warming up and moving around takes alot of energy (energy he is not replacing because he is not eating/eating very little). So, for the sake of your tegu, just let him sleep and be patient. He will wake up happy and refreshed and ready to party for the summer.
In nature they hibernate each year in most parts, so they are biologically programmed to follow their instincts to hibernate. They will never breed if they miss even 1 year hibernation, its that important to them. They also detect things like light cycles=outdoor temps, and possibly even barometric pressures/weather patterns even if kept indoors and warm. Remember these are creatures of instinct, and each is an individual. Vito, my 3'4" Arg BW was hibernating when I got him, woke up in late February, and has been very active ever since. It is pretty cold here in KY right now, but he shows no signs of slowing down. Many people have tegus that hibernate each and every year at the same times each year, then some have tegus who hibernate every 3rd or 4th year. They are all different, and each will do whatever it feels like doing.
Sorry to post such a long one, but I already answered this kind of question twice, so I am just going to refer this post to any other questions about hibernation. It seems like a lot of the experienced people, people I learned alot from, no longer post here. So for the sake of the tegus, I am still hanging around and putting in my 2 cents. But I wish these guys would come back so you can hear this from them. Please do a search (the link is right above the Post New Message link) or scroll through the past posts and archives and look for the following names (I am sure I forgot alot of good folks, but these guys respond to a lot of the same threads)
Rollin
RussXXXX (XXXX is some number I don't remember)
BeardieDragon
AsiaXXX (another series of numbers I don't remember)
KingOfSeattle
BeuesBlue
BlueTegu
Stella St. Pierre (her husband posts also, they own BlueTegu.Com/AlbinoTegu.Com and are pioneers with tegus)
And plenty more who you'll no doubt notice. I am sure I drove some of these guys crazy with some of my questions, but they were always helpful and stern when necessary. Anyway, I hope this helps.

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-Bill
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