Hi, if you have informed your team leader about you that you are not able to continue due to your illness and required leave, you just have to submit your all prescription/treatment and other relevant medical bills to your HR. But you must have taken the permission from his bcz you have to work under him in your return.
And as you said that your experience with them is not good, then you must look for a new job after some time and dont care about it ...but if you are making excuses of your illness and are worried about this bad experience with them, i dont think you are at right path..
Coming to the point, in your return when you will present the valid reason and your complete treatment/prescription/bill and other relevant medical documents to him, surely he will understand your part and will approve your leave. Also you have to present the same document to your HR for their work ..your Team leader cant perform the job of HR personnel but can give you more bcz you have to work under him in your return. Think about it first.
Now you need to take proper medication..Take Care and Best of Luck