No it isn't. I am not quite sure what you want to say. The first part should read "I feel younger today than yesterday" but then after that I don't know if you are trying to say, "but I will feel even younger tomorrow". It's not really an expression we would use.

I think the expression is "I feel older than yesterday but younger than tomorrow." I am not sure if there is another way to express this. You could certainly say that you feel younger than yesterday, but as Joanne said, the second part doesn't fit, because it's not usually said that we would feel even younger tomorrow. So I think what you are trying to say is what I wrote in the first line.

Puedes escribir esta frase en Español? I may be able to help translate to English. I think Carol's comment may be correct.