Hey if it's not too tight, I am sure you will get used to it pretty soon, I hope your mum got you a soft and simple one, the lacy type with frills will surely be uncomfortable ... You wearing it out to show? Trust me... Guys love it! I for 1 has something going for girls in this! I won't be pulling it! Enjoy!
Yeah they are made to rest against your anus. The size you get matters and so does the brand because like pants they are all made to different dimentions. Make sure the waist bands are high enough so that when you bend your legs it doesn't pull it up the back making it un comfortable. The back strap should rest but not be tight across your anus. Once you learn where to adjust it when you first put it on you won't even notice it.
I know how you feel. My first time in a thong was when I was 9 for dance. my teacher said that we should wear thongs under our costumes so my mom put one on me while helping me get dressed. I remember feeling very awkward not understanding what was happening with my underwear. I kept squirming backstage trying to remove what I thought was a wedgie.
I didn't wear thongs again until I was 14. my body was more developed and my friends all wore them so I was more ready Now I were them all the time and like the feeling.
if you find thongs uncomfortable try waiting a while then wearing them again.