I really like someone, they have made ne feel like this, but also they have a partner.....ans its driving me insane, i cant stop thinking about them....its stopping me from sleeping help??

I've had experience with this before and it's no easy task or something very easy to handle. It's okay to like someone and it's normal to have feelings for people because as humans we can't control how we feel towards other individuals. What can be detrimental is if you intervene in their relationship. The reason being because it could lead to a dangerous situation where the partner gets mad and tries to harm you or it could harm your mental health if you face rejection. I would say maybe talk it out with the person you like and let them know you have those feelings for them, or maybe asses why you like that person and how they make you feel?