I’m 13 and a 36E cup. Should I do anything about it?

a good quality bra and Advil. Good luck Kira.

If you get older and its still really a bad problem and you feel like you need it fixed set up a gofund me or something. There are woman on there asking for help getting breast reduction surgery and although they dont always reach their goal they do get a few thousands dollars to help them afford it.

yes. you can buy the right over the shoulder boulder holder . Most pain is caused by ill fitting bras.

Yes- wait until you are 18 and see if your body catches up to your boobs. If not then you can discuss breast reduction with your doctor.

If you live somewhere where health care is a right and not a privilege then you can have it done for free if they are physically hurting you

Weight bearing exercise, ie weight lifting will help the neck and back pain. Start with light weights, build up over time (you don't want to overdo it at first seeing you already have a lot of muscle access to deal with). 

Motrin and Naproxen are similar drugs (same family). They are fairly effective for period pains. Choose one of those. 

If you are still having pains, you can Tylenol on top of one of them (Tylenol is compatible/safe with Motrin or Naproxen). 

Also you could try getting fitted at a high end lingerie shop. A GOOD fitting bra will help with every day pain.

Advil. It helps a whole lot