sighs... it sounds a bit like you've stretched one or both of the multimeter's leads.
have you tried shorting together the multimeter's input terminals directly using a short piece of copper wire? if this reads (close to) zero ohms, then the problem is in your leads. do you have a spare set to try?
if you stretch a multi-stranded length of cable (such as a multimeter lead) that has fine strands, various of the strands within the cable will snap. they will NOT all snap at the same place. the end result is that you can, after a few minor stretches of even fewer major stretches, end up with a length of cable with no single strand being connected at both ends. this will result in... well, i hope yo can imagine the result! volts will usually read fine, ohms will have a disconcerting offset, and amps will cause the damaged lead to get unexpectedly hot.
cheers,
rob :-)