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?

1) I have a large amount of course work, which is combined with a job and extra-curriculars, and while I want to succeed in all of them, I find that I simply don't have enough time, even though I currently sleep only 4 or 5 hours a night. I mentioned this to a group of my friends here at school, and it turns out they all take stimulants to help them manage jam-packed undergraduate life. The pills are called ADDERALL and PROVIGIL. I have acquired some for myself, but before I take them, could you tell me if either has serious health risks? I do not have any other health problems or take any other medications. A few of my friends tell me that they sometimes stay awake for as long as 3 or 4 days. If it is reasonably safe, that would be great! Thank you.

2) Given the fact that this is a top-notch school, it's total hoo-ha that you haven't included any info on all the non-hard core, but still illegal, "study stimulants." Is all this ADDERALL gonna do me permanent damage or what?

I have been taking between 5 and 10 mgs of methadone daily. I cannot seem to stop. Every time I try, I get very, very depressed and experience abdominal pain, chills, hot flashes, and sleeplessness. The depression and tremendous anxiety are intolerable and I end up taking more to avoid it. Question: Am I harming my body and/or mind with this stuff? How can I get off without the horrible feelings?