Blood cancer (Leukemia) Reply doctors.

A teenager girl, having pain in the left side of my chest near heart for the past 4 months , got heart tests like Echo , ECG done , but the pain is still there with me , Sometimes blood , mucus comes in stool ( once a fortnight not very often) , weight fluctuates even after eating same foods, extreme tiredness, fatigue , and till now two times my ankles have swollen, nose bleed a little only once today.. Cardiac reports don't indicate any flaw , but I feel like my symptoms are with leukemia, by the way , I have my appointment with a grd doctor ( gastroenterologist) because parents are suggesting instead of any serious disease all this is included in grd disease, want to know what I can do.. please reply doctors..