Talk to your mother and your father; discuss this with an adult relative with a good relationship with mother, maybe the situation will improve. If not, Father must file for modification of custody. If the judge asks the ultimate question of where do you want to live, your opinion will be of interest to the judge, but you do not get to choose. Your reasons must be sound and not self-serving. The judge will give your opinion the weight he believes it merits. The judge may not ask where you want to live; he/she may just ask how you feel at one home versus the other, what you do there, etc.
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Attorney Whittaker has made some great suggestions. Additionally, if you are feeling overwhelmed, anxious, or depressed, you may want to seek out a counselor at school (if one is available) or tell your parents you would like to start working with a therapist--not only will this give you a neutral person to talk to about how you're feeling, but they can often serve as a facilitator in a discussion with one or both of your parents to help you express how you're feeling to your parents. Recognizing that you feel this way is mature and important, the next step is to seek out support so that you can start learning ways to cope with it.
As Bill said, you don't get to "choose" but you can talk to the judge and your opinion will be given weight. Your Dad will need to file paperwork for that. The judge looks at all the circumstances around a change in custody. Talk to your parents and maybe you can work something out. Summer is the perfect time to try a new arrangement.
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