My feelings for someone cycle through intense love and indifference. One minute I'll be clingy and lovey with my girlfriend and the next I'll act as if I could care less about our relationship. I also hyper analyse everything she says to me so bad it paralyses me mentally; my emotions and internal view of her change radically based on meaningless conversation.

How can I relax and not get so emotionally involved with my personal relationships? Is there some neat label like OCD or what have you for this?