No lamictal doesn't cause sexual side effects. It's probably your underlying condition of bipolar disorder or depression itself. It doesn't affect serotonin like the SSRI antidepressants which cause sexual disfunction. Instead it works through and independent mode of action acting as an antagonist at the NMDA receptor. YMMV, though.

Lamictal has been an excellent mood stabilizer for me...few side effects once it's titrated up to a theraputic dose without problems.