Im 17 and I've been stuttering my whole life. Honestly my best advice for getting over the low self esteem is to understand that it is something you cannot help. Its out of your control so you shouldn't beat yourself up about it. Everyone has something weird about them, no one is perfect. Your speech doesn't dictate your intelligence, know yourself and be confident in your abilities. Some people will laugh but I those times are very rare. Coming from someone who is still in high school, I've only had people be rude about it once or twice in my entire high school life. Most people don't care and will still appreciate you for who you are. Not in spite of your stutter but they will care about you stutter and all because that is who you are.