2 months no period, pain sometimes with sudden movement, noticed periods were lighter 3mths before i had my first missed period. negative pregnant tests?

Medication related?: Are you on any new medications? This could be affecting your cycle. Also, You could have a polycystic ovary which would explain the pain and irregular menses. There are some other things that can cause these symptoms so get to a gynecologist right away to investigate the cause further. You may need blood tests or an ultrasound.

Needs evaluation: Especially at younger age (ie. not approaching menopause) this can be easily evaluated by blood tests to determine if hormonal abnormality, and a pelvic sonogram to look for an ovarian cyst.