Allogasmia is the condition of being unable to orgasm without fantasizing about an individual other than your sexual partner. It's a pretty common condition, and not necessarily a problem.
Restless Genital Syndrome (RGS), also knowns as persistent genital arousal disorder (PGAD), is a condition of spontaneous, persistent, and uncontrollable genital arousal, unrelated to any feelings of sexual desire.
For some sufferers orgasm can provide temporary relief, but the symptoms of arousal soon return. The symptoms can be so severe that they are debilitating and prevent sufferers from leading a normal life.
The syndrome is painful and distressing and was newly added to the DSM-5 in 2013. But causes and treatment are still being investigated.