Thanks for your consult at DoctorSpring.com.
Endometriosis could be responsible for your symptoms - heavy menstrual bleeding, heavy cramping mid cycle and spotting midcyle too. Other than that , the possibility is that you are having some condition such as a uterine fibroid ( benign tumour of the uterine muscle ) or endometrial hyperplasia ( thickening of the lining of the uterus ) or adenomyosis ( thickening of the wall of the uterus ) or uterine polyps.
All these conditions are caused due to excess of estrogen, just as endometriosis is caused by excessive estrogen levels.
The ultrasound scan will definitely diagnose all of these conditions easily, so please wait for the results.
Also, at your age, cancer is quite uncommon, nor are the symptoms in any way indicative of genital cancer. Endometriosis might be missed on ultrasound, but the diagnosis is easily made clinically.
All the conditions are readily treatable, except for endometriosis, which is notorious for recurrence.
Sometimes, stress, anxiety, hypothyroidism, polycystic ovaries, travelling, weight gain, ingestion of hormonal medications - all these also could cause heavy periods.
I would have advised you a thorough gynecological evaluation ( per vaginum and per speculum ) and a pelvic transvaginal ultrasound. This will reveal the diagnosis. Please do get back once you have the scan done.
All the best.
Please feel free to ask for further clarifications.