Welcome to HCM
Your description pain is like you have colic which can be due to kidney stone some where in the urinary tract
, painful urination could be part of colic or if you also have burning and frequent urination
it may point towards infection that is UTI.
As you have started period also some times pain of spasmodic nature may be attributed to period but unilateral nature of pain goes in favour of Renal Colic
Please visit Hospital/Surgeon who will examine and a Xray KUB and Sonography
of abdomen would give cause of pain,a CBC and Urine analysis will help to know infection.
For pain you may take simple analgesic like paracetamol
Good Luck to you