I have had a stutter since I was 6 yrs. old. Like you it was worse under pressure. It did ruin my self esteem and made me isolate myself and fear talking. Two and a half years ago I got a job where it was occasionally expected of me to make phone calls and also to speak to medical professionals. In the process of being forced to repeatedly complete these tasks, I lost my fear and gained confidence. So I challenge you to put yourself in a situation where you have to talk. You won't loose your stutter but it will improve and you will be living your life instead of hiding. I know this is especially hard as a teenager but please don't waste decades being afraid to order lunch like I did.