Suggest Treatment For Irregular Menstrual Cycles And Under Developed Breasts

Hi. I'm here to ask about 2 questions. First, I want to know if stipend as a residency trainee is enough to support daily needs. Next, I want to know what the problem is with me because I am 15 years old and I am quite short with really small breasts (Less than 32A). I also have trouble with my menstruation since I've missed 4 months of my period, had it for one month and lost it again for 2 months now. I am about 5'1 and approximately 90 pounds. I eat a lot but I don't gain much weight anyway. I think I have hormonal problems. What should I do?