My periods are usually once every 3 months, but i've had 2 periods this month. What does it mean?

Somewhere between oct. 31-nov. 1, i got my period (i had major cramps the 31 of oct-so i knew it was coming). Usually, I am lucky to get a period once every three months. The one that started around the 1st of nov., was like my usual period, heavy at the beginning with uncomfortable cramps, then getting lighter mid way through (only lasts around 7 days normally). But, on dec. 1, i had another one, but it was so light and dry(more brownish and almost a little gooey) that i barely need to wear a pad-there was only a little on my underwear and there were no cramps at all and it lasted around 5 days, but it seemed like each day after the 1st of dec, it was getting just a tiny bit heavier until it stopped around 4-5 days later. Now, (a couple weeks later) i have been finding more of a brownish discharge on my underwear the past few days-it was very light and dry and didnt show in my urine, but each day it seemed like it was getting more red and a little heavier. Today(Dec. 21), i had a stomach ache for a little bit and i still have no cramps to speak of, but now its like a period, only not as heavy-its very light. This is VERY unusual for me. I never get periods, but this month its twice in a month and its starts off brownish and light and gets more red and heavier (it should be the other way around). What's wrong? Is it something serious? I have a family history of diabetes and a couple months ago, i lost about 6 pounds and i do take Vitamin C supplements and two medications. I dont know whats happening.