What Cause Periods To Be 40 Days Apart?

Hi
I'm 27 years old and don't think I've ever had a normal menstrual cycle. Previously a semi-pro middle distance runner I would miss my periods often and if it occured it was minimal and lasted a few days only. After stopping competitive running, it seemed to start occuring more often however lately I've started counting days in between and have realized my last 3 times was approx 40 days apart. My cycle also only relative flow for 2 days where after it mostly spots for another 2-3 days. Is this normal? What should I do? As a runner I battled often with low iron levels so I suppose it could be a risk factor again. I still remain active running, cycling and swimming every other day but in moderation as oppose to wheree I was. I weigh 54-55kg and am 1.7m tall.I. Have been on hormonal supplkements a few times but never kind of liked it so would discontinue it after a while. Just like to know if I should worry and maybe go see a gynochologist?