Crowding, malaligned, crooked, rotated teeth does have affect on your muscles, jaw, TMJ eventually causing stress and headache.
You need to take an OPG which givens overall hard tissue view of your jaw and teeth. Cost of reshaping treatment can only be told after seeing your radiographs or clinical pics. Visiting a dentist in person would help you more appropriately.
Next Steps
Visit an orthodontist for reshaping of teeth
Health Tips
1.once a tooth decayed, it needs to be filled. any preventive measures taken is only to further stop spreading decay to adjacent teeth. you need to have a check on your oral hygiene too. brushing twice daily before breakfast and night before going to bed is must.
2. avoid in between meals snacking and even if having make sure you gargle your mouth with water at least.
3. visit a dentist at least two times in a year for checkup