Turn Signals / Flasher Troubles

Over the last 6 months the turn signals on my Rodeo (99 4WD LS) have slowly joined forces with my emergency flasher lights. Now when I turn on a turn signal, both come on as if I were turning on my emergency flashers. At first it only happened occassionally, but now it happens every time I try to use the turn signals. All lights work so it doesn't appear to be fuses or lights.
Has anyone else had a similar problem or know what the problem may be....and how to fix it? Thanks for your help!