The I am a 31 year old women, and the outside of my throat hurts below the adams apple, with itching by the collar bone and slight weight gain.

May be ur thyroid. It could be a goiter (small or large mass on the neck), thyroid nodules, or cancer or something else. You should go to your primary care doctor and get bloodwork (tsh, t3, (liothyronine) t4) and get an ultrasound of the throat area and possible biopsy.. With weight gain, i would suspect you may have hypothyroidism, which goes along with the goiter. It may also be nothing. It is hard to say online.