spotting

So, a couple days ago I missed my pill because I worked all day and just didn't think about it :-( I've never spotted in between periods but because I missed my pill I started spotting yesterday, no big deal. However, it's kinda heavy and I was curious if anyone has any advice? How long will this typically last? How heavy should it be? It didnt look like blood, just brown stains until just now, it's starting to look like period blood, but enough to fill a light tampon after about 90 minutes :-(