The elastics that orthodontists prescribe to be worn with braces or aligners are used to move a tooth or a group of teeth in a particular direction, or to correct the bite. In the first week after you start wearing elastics, you feel increased discomfort and pain in the teeth they are hooked onto. During this period there is less discomfort with the elastics in than when you take them out. After about a week of wear the discomfort subsides, and after two weeks the feeling of tension and pulling from the elastics disappears. Many patients who wear their elastics regularly tell us at their next appointment that they can't feel them any more and ask for stronger ones. In fact, the elastics are strong enough – the body simply gets used to the irritation and learns to ignore it, in the same way you get used to wearing a bracelet or a watch.
This answer is for general information. Your own case needs an examination by an orthodontist.