The rapid weight gain combined with the mood swings suggests that something happened around the time of finishing high school and the beginning of dating. As the physician may only be looking at this through the physical and medical lens, you may want to have a therapy session with a clinical psychologist who can help explore through testing and therapy what may have been going on during that time in your life. The fact that there was a major transition with the people you were with in high school to your boyfriend would be a place to start. I’d pursue individual therapy to see if the therapist can help you sort through what’s underneath these frustrations.
Wishing you patience and peace,
Proof Positive Blog @ PsychCentral