Could you possibly tell me the interactive effects of Zoloft (the anti-depressant) and MDMA (Ecstasy)?

I am a teenage girl currently taking Adderall (20 mg) to treat my ADHD. My question: does taking this medication affect sexual wantings or behavior? I am supposed to start taking it at 7:00am so it will wear out at about 9:00 or 9:30pm. Since I go out later at night, my medicine is usually worn off before I engage in any kind of sexual activity. But sometimes on weekends I wake up late and have to take it at later times such as 12:00 or 1:00pm. Since then it will not wear off until after I go out, would being on Adderall affect my sexual behavior? I feel like I am less "horny" when on Adderall and sex is worse because of the lack of my desires. Does this have anything to do with my medicine or is it just a coincidence?

I originally took a muscle relaxer because I was experiencing very bad back pain and could not sleep. I was not prescribed the muscle relaxers. My friend suggested I take one of hers. So I did, and now I will take one sometimes before bed if I can't fall asleep or if I want to actually just relax. It makes me just want to sleep, and I feel really calm after taking one. Is this bad that I take them for this reason? What are the side effects? Is it harmful?