I am not sexually active (never had intercourse), but my menstrual cycle hasn't been regular for the past month. In the past month or so, I had 2 subsequent periods with only a 2 week interval (ovulation period) between each--my last real period (red blood) was a lighter flow than usual, and ended 2 weeks ago, but now I recently noticed that I have a brownish looking period (light flow) that has lasted for about a few days.

Is this normal? Are my hormones playing a role in this? I started my period when I was 13, and now I'm 18, but my periods still go through an unpredictable, irregular cycle.

I hope it isn't a sexual infection... or pregnancy?

Have you ever had the injection or the like?
Or anything else that could have effected or changed your hormones?

No.

The reason I mentioned hormones was because I have read around that the irregularity in a menstrual cycle could just be the hormones still balancing out while developing.

I'm experiencing the same too! I'm quite worried to be honest, and I am in the same position as you. I have neva had intercourse and after two weeks of my last period I had brown discharge. I don't understand why and I hope it is nothing serious. :( my periods are also irregular, as I had a period within two weeks of my last one. If you do find out any information please let me know.

If u haven't been sexually active there is no way you could be pregnant.. since your periods are irregular it probably is old blood cleansing away also check for Urinary tract infection..