It is different with everybody, but it can go away/fade on its own. Working on the anxiety may help it go away as the more you worry and "poke at" the symptoms mentally you tend to reinforce them, so learning some relaxation techniques and if you need it getting treated for the anxiety should help and will make any illness you ever have easier to cope with. Anxiety usually makes everything else much worse.Do you eat more than enough calories to gain weight? It may be worth tracking your calories to make sure you are eating 500 calories more a day than you need. If you are a fidgety person always moving something (some anxious people are) you can burn a lot of calories so may be underestimating how much food you need. There are a bunch of online calorie counters that are free that you can track your food for a few days and that will help you figure out how much you need to eat to gain some weight.If you cannot gain weight even when you eat 500 calories a day more than you need (and 500 extra calories a day should put on one pound a week, so do that for a month or two to see if you can gain weight doing that) you should be checked out by the doctor. You might need to be tested for celiac disease and some other things to make sure it isn't just a not eating enough problem.Some people just have high metabolisms and really have to work hard to eat enough to keep the weight on. If you tend to avoid eating when you worry (some people do) that can make it very hard to get enough calories in. Also if you don't eat as much when you feel gassy or bloated (also very common) that can also make it hard to keep the weight on.