Birth Control Inquiry

I started taking Aviane (generic for Alesse) in Early December. It's been almost exactly seven months since I've begun taking it and today I had a bit of breakthrough bleeding / spotting (I'm not sure which term or if they're different). Just very light bleeding. It didn't come off in my urine, it wasn't heavy enough for that, but it did come off on the cloth. It came immediately after sex (that was a tiny bit rough; excuse me, I thought it might be necessary to mention), so I thought that perhaps that was the culprit (but I don't know if that's possible). It only lasted an hour (it dulled down and has seemed to disappear). I have one pill left on my pack before the blanks. Sites I've seen have said that pill types should be changed if spotting lasts for three or so cycles. I've never spotted before, so I did some research. Some sites said that it was common for beginners-6 months (7 is pretty close, right?) and can also be induced by things like stress. This month I've been kind of stressed from work, getting a puppy (something I've never had before, and she's a huge handful) and (mostly due to her) not sleeping very well the last few weeks (having to get up several times during the night, getting woken up early, generally being very tired and exhausted in the morning from not sleeping well). In fact, the last couple of nights I've gone to bed at 5 and gotten up at 10. Also, last night I took the pill two hours later than scheduled.

What I'm asking is the likeliness of this very brief spotting (note: no tender breasts or nausea or cramping) being birth control (stress-induced and whatnot) versus pregnancy. The pill I'm taking, I believe, is a weak one. Should I apt to get a stronger kind to avoid spotting? I've been advised against sexual contact during or after spotting because of the low hormone level could cause one to conceive. I just need some information before I see my doctor.