Hello
As you mentioned that there is
sharp pain on the right side ( lower abdomen ) .
You are also having irregular , light , spotty period for last 3 months .
Now also irregular period ( 15 days before period date ) .
All these symptoms ( you are is just 26 years ) may be due to these possibilities .
1 Poly Cystic
Ovarian disease ,as this may be the most common cause of such symptoms , so please get in
ultrasound of both ovaries for confirmation , so consult a gynecologist and get his opinion.
2 Hormonal imbalance causes some times this type of pain and bleeding so get in FSH/LH tests .
However , there are so many other reasons of such pain as right renal calculus ,
appendicitis ( chronic ),
salpingitis but in your case most probable reason may be PCOD .
So first rule out this and consult a gynecologist .
Good luck.