So ganas while being 2nd person singular present, it is not functioning as that when combined with tengo. The phrase is I feel like which I take is an idiom.
"Ganas" is a noun, not a verb, therefore it cannot be in the 2nd person singular...The verb in this sentence is Tengo. I typically think of "ganas" as a desire. In this case, "I do not have the desire to eat" also could be said I don't feel like eating.
Ok so in this case ganas isn't a verb 2nd person singular because that would be referring to winning or earning which obviously isn't the case here. So it's to 'have' 'the feeling of desire". It's hard to get my head around a feeling of desire as a noun. But my thinking doesn't work. Strange.