EXTREMELY weird Eating habits

[iHazSnake]

So a while back a got this beautiful nicaraguan boa. He has been eating fine, hes about 4 1/2 feet... eating 1lg rat a week. THen all of sudden he stopped eating, became very aggressive,(He was never, he was braught to a carrer day event where 300 kids played with him, he was such a sweet heart) and also always has a foot of his body going up the side of the tank, and will stay like that for hours. I tried feeding him every week for 2 months, with no success. And one time he actually went for the rat, and i am not exaggerating but he missed 17 strikes. then a couple weeks later (Which would be today) i tried a small rat, and he just stared at it for hours, and the rat even went to sleep, so i left him in there together over night, ( My snake could hold its own against a newborn rat) and when i woke up it looked like he had killed it eaten, and regurgitated it. i Have no idea whats up with him, i think i am just going to take him to the vet, but i was hoping mabey some of you guys could help a little bit.