how much cardio is too much

[anotherway83]

it takes me FOREVER to make the slightest gains in strength+size so anything that makes me lose weight gets me worried heheh

so i've been doing a good deal of cardio the past month and i've already lost 6 lbs., i was only doing it to get my abs to show, havent lost any strength yet but at this rate i think im gonna start losing muscle soon

how do i know how much is the right amt of cardio.

thanks