Is there any chance I could be pregnant?

Okay, I did some traveling in June and came back June 23rd. My last period was June 21st. I've also been under a considerable amount of stress a few weeks ago and during my trip and a few days here and there. anyways, I was due on the 18th or 19th as I tend to have a 28-29 day cycle. I'm 16. I'm a virgin, but I do fool around with my boyfriend sometimes. The only thing I can think of is that I got some semen on my hands, but I wiped it off or it was dry before I went to the bathroom or anything. He has fingered me before but I don't think he had any wet semen on his hand. He would have known better. And we have ed before but we had all of our clothes on. Anyways, today is the 15th and I noticed my discharge was more abundant and it was bloody, kinda brownish redish. It's lighter in flow too but not too light. My period did this in May though, it was like this the first day and then the next day was more flowing. This isn't implantation bleeding is it? Or am I just paranoid?