Why does my right side lower abdomen hurts when am aroused?

Arousal involves increased blood flow to the clitoris, but also to the female organs such as the uterus and ovaries. It may be that if you have adhesions from a previous surgery, or an ovarian cyst, or even a light uterine ligament, you may feel a pulling or ache in those areas. Talk to your gyn about this.

This is an unusual corelation. But if it persists you need an exam by Gyn for proper diagnosis.