14 year old, heart burns, acid reflex, stress, out of breath, can this be cancer or stress?

Im 14 years old I have been having abdomenal pain (around my belly button and a little up ) and nausea for the past 4 years This all started 4 years ago the day of my maths exam ..I am not allergic to any foods not medications but my mother,brother and I suffer from migraines.I have done several tests for urin faeces and for lactose these came out all negative but the faeces one came a little bit over the normal amout ( I don’t have any blood with my faeces or anything) so the doctor recommended a colonoscopy and the stomach one (I’m sorry I don’t know what it is called) the stomach one came normal and the colonoscopy showed a little swelling in the large intestine which the doctor said that they don’t know the reason behind it .. so my doctor recommended that I cut all milk products,cheese and eggs which isn t really making a difference. I also have un regular periods I have only had 3 periods in two years and my obgyn scheduled an ultrasound. I suffer as well from stess I stress for the slitest things .. since then I have been having these Heart burns and what I think is acid reflex no kind of medication worked (my father also suffers from hurt burn and acid reflux), dizziness from the smallest things like people walking and when I stand up (my doctor said that it might be low blood pressure) and since I have scoliosis i have a back brase which I think causes me to when I climb a flight of stairs I have no oxygen and can’t breath . Sometimes when I am on the bed my hearth starts racing like I after a race (my mother has heart problems since she has a hole in her heart) . So my question is if you are familiar with my case and if you have any idea of what I have?can this be cancer or is it stress? Thanks for your time ?