What is meaning of tainted love?

Answer
The lyrics pretty much describe a romance where one individual has given more love than their partner. They are losing faith that this relationship will provide them with the healthy rewarding love that they covet. The song is a their message to the partner that they have had enough and are essentially running away from a love that has turned sour and is no longer fulfilling.

Answer
I don't know about lyrics, but the expression, 'tainted love' means love that has been spoiled by something. The use of the word tainted, is in the context of contaminated. In the context of love, contaminated love, usually refers to a relationship that has been spoiled by a breech of faith, a relationship begun under false pretenses, or a partner in the relationship can't or won't let go of a prior, or destructive relationship.