First of all, if it's affecting you, making you upset or affecting your day to day life then it is important and you completely have a right to feel upset about something that you find upsetting - any feelings you have are valid.
Personally i think being open and honest with your family can help immensely; even if its just one parent/guardian or a sibling - getting it off your chest can feel like a weight off your shoulders. Also if it's health related definitely go to your GP and see if there's anything happening there.
Also i feel like its important to know that many people have insecurities and so there are a lot of ways to handle them, for example, there are CBT courses or other counselling/therapy courses you might want to go to. There's nothing wrong with going to therapy, I know that there's still somewhat of a stigma around it but if it helps then you shouldn't ever feel ashamed about needing it.
It's also important to remember that being so aware of something yourself can make you feel like everyone else notices it too, when in reality only a few people may notice it and in the end they may not even care. If the comments make you feel insecure, there's nothing wrong with telling the person that you would prefer they don't mention it - most people are not dicks and will always take your feelings into consideration.
On a day to day level, one of the most important things is focusing on the positive relationships you already have with your friends and family, not your insecurities - although it will always be hard to ignore that little voice in your head, sometimes it helps to focus on one thing at a time.
go to your lessons, learn, find the small moments with your friends at school. Don't make extravagant plans, its alright to just hang out at home and chill - but try not to let this stop you from doing things that you want to do. Try and fill your days with things that make you happy and just try to forget about it all, even if its just for a little while.
I hope this helps, I'm not that great giving advice but I thought I could at least try
xxxxxxx