7 day light period...?

I am trying to get pregnant. I have unprotected with my fiance several times per week. We have been trying for 5 months. This month, my period came on time. I had only 1 slightly heavy day. The rest were fairly light. Usually I have 3-4 heavy days and my period lasts 5-6 days. The only other time I have had bleeding for more than that was when I was pregnant but miscarrying. It was very heavy and painful then. I usually have cramps during my period and they are fairly bad but this month I barely had any pain. It is 7 1/2 days and I am still having a little bit of bleeding. Since I got my period, I don't think it is possible to be pregnant. I have been getting my period for 10 years and have not once had one like this. I know cycles can change but I am always regular. My period comes between 24-26 days and it was 25 this month. My periods come on like clockwork and go away the same. Does anyone know what could cause an extra long, light period? I figure some of you girls TTC may know a lot more about periods so someone may know what is going on. I know I should take a pregnancy test to be sure but I don't think there is any way for me to be pregnant since I've bled already this month. Thanks.