Questions about diet pills?

Have some questions about diet pills please answer to the best you can. I need to lose some weight with in a few months about 4 or 5 and I have a bmi of 29.1 So here are my questions. (I also do not want to have any loose skin.) I have tried many diets and exercise but nothing seems to work.
1. What is the best die pill that is also cheap?
2. Is it safe to buy diet pills off of the internet?
3. If it is not safe to buy them off of the internet where can I get them cheap?