Longer period than usual

[Chickenwings85]

My periods have always been pretty regular until around 18 months - 2 years ago where they disappeared for awhile and then come and go as they please.
I have mefenamic acid to take for the pain on the first and second day of my period which is when it's the worst. I also use them if a headache gets unbearable which will usually delay my period by around 5 days or so. I took 2 of the mefs for a headache around 2 weeks before I was due on but this time it delayed it by over 2 weeks! My periods tend to last around 5 days. The first signs of my period was when the yuk brown stuff you get at the end shows up, I had this for around 5 days before blood started to show. It's now day 14 of this 'period' since the brown discharge and I've had low pain period pain most of the day but also starting to feel dizzy with it now.
I'm just wondering if anyone else has experienced this and what it was?

I would seek further medical advice from the GP.

Have they tried to work out exactly what the cause of the period pain is rather than simply give you tablets?. Brown (old) blood and period pain, particularly if that is cyclical in nature, could be due to endometriosis.

Sorry, did you mean you had this light period after taking those tablets? When I was on those they made my periods bleed lightly and irregularly.