Do you have a Saturday job? Maybe this would be a good starting point. Depensing on your interests, try local shop, riding stables, hairdresser, buidling site, newsagent and see if you can get anything suitable.
This might help to earn you a little bit of freedom, independence as well as some money. Mum wouldn't be able to text you every hour if you were at work as your phone would be out of bounds until your break time. It would help her to gradually reduce the contact and start to let go safe in the knowledge that she knows where you are.
Second question - have you ever done anything to cause her to worry about you in the way she does?