My cat was missing for 2 1/2 weeks and came back tonight. He is acting a bit odd & i need some opinions/help!?

He is a maine coon who had left the house for almost 3 weeks for his first time. Tonight i was out on my back porch and he randomly came back. He was meowing a lot and acting very scared. It took a while before he went inside. Now he is still meowing loudly and a lot and is roaming around the house. I tried giving him food, some of which he ate, but i dont know what else to do. Could he be sick? Or is he just homesick?