I have been using a micro SD card for some time in my phone and all of a sudden it stopped reading from it. If I mount the card again will I lose all the data on the card?
No, but if the phone stopped reading it, you may not be able to read the data on it. Install SD Insight and make sure it's a legitimate card. (Also check the date - we didn't have that technology in 1970, so the card WASN'T made then - if it says it was made in 1970 it's counterfeit and will stop working as soon as you fill it up to its REAL size [which could be 2GB].)