me again. I feel that not many others will speak, as this is really a board for tug that include 2 or more people, and also due to your age. But i don't mind, its better to be told a good way to tie yourself than to experiment and hurt yourself (which i did once... continues loop of stretchy fabric, no end so no knot.... placed it above my elbows behind my back and coudent get it of as it dug into my arms.....) so i don't mind helping. But i would need some more information about what stuff do you have?
Do you have any more stuff than what you listed in the first post. Also what are the lengths of the cloth belts.....and how inventive do you mind getting? 
here is an idea to create some rope, not tried it out yet, and probably wont to be honest but i want to know if it works if you try it....
carry bag rope - get 5-10 carry bags, pull them tight, so the handles are both in one hand, and the end is in the other, so they are thin. Then lay them out, all facing in the same direction, this may seam a bit long at first, but knots will shorten it as you do the next part.
Use standard knots, 2 on each bag, one BELLOW the handles (for strength, wont be fun if they brake when you struggle, and DON'T plan for them to brake either) and then one on the closed end, BUT make sure that it includes both that bag and the next one, this way you join them together to create a long rope like object. This will not be conferrable to use, but it can be good to get a long length. As they are carry bags, they will go to a small space and will their forth be easy to hide in your room.
If you get stuck and have to cut it or if it brakes, then get a new bag and replace the broken bag, carry bags are easy to put into the bin without people thinking anything of it, what i always use to do for any bags that i played about with is, i would keep a bag in my room for all of the rubbish, this would slowly build up, and when i had something i would need to get rid of, i would put it at the bottom and put it into the wheel bin myself, no one would check a bag full of rubbish. It is how i get rid of most of my 'experiments' that i have.
Well, until i get the more details, i cant really help much, i know a lot can change in a couple of months....
Also try to think of anything else you can use, don't have to be anything special, like the bed sheets, but also towels can be used in the same way. Only thing is to remember what the material is like, one that can stretch can be good to get into, but if you get stuck their a pain to get of....as knots tighten a lot on them...
So, when i get more info then ill come up with some more ties. Now im of to get inspiration

p.s. ok, something else that i want to add....can you tell me info on the envirment that your tieing yourself up in.... This is as i just tried something myself, had fun but then i nearly fell of my bed onto a table.....just dident fall of and dident have my arms free to brake my fall so i got very lucky.... I am guessing that it if in your bedroom, on the single bed, if not please say.