(Not a teacher)
Both are the same, yes. Although, the second could be used to mean 'I feel like the way I do when I have a fever'. The first cannot be used this way.
Although the first is more definate - 'it is definate I have a fever' - it sounds strange to my ear. I hear 'I feel like I have a fever' much more often, even when used definately.
Nightmare85, 'some temperature' couldn't work. You can't 'have' temperature, per se. The word 'temperature' is used, in British English at least, to mean 'fever', but it would be used in the same way as fever, i.e., 'I feel like I have a temperature'. The way you used it, it means temperature in general.