(TMI WARNING) Help! I don't know what my vagina is doing again!

So I'm worried that something may be really wrong with me. I've had very irregular periods for about a year now. Sometimes I won't get one at all for a couple of months and sometimes I have light spotting. I would say that I haven't had a "normal" period for maybe 8 months or so. They used to be very regular and medium-heavy flow. Now they're very light but last for about a week. Today I saw something that I've never seen before. My underwear were very wet and had a little bit of blood (it looked as though it was blood that had been lightly washed away with water). However I was very alarmed as I had very thin, watery very light yellow/green discharge. I can post a pic if necessary. There is NO way that I could have an STD as I've only slept with one person and I'm the only one he's ever slept with. I'd like to think that I take pretty good care of myself (I always pee after sax, I don't use harsh washes, I NEVER douche, and I am a huge fan of using feminine wipes regularly as I like to feel "fresh") Have any of y'all experienced this? I'm really worried about it.