Could I be pregnant?

Okay, so im a little confused here!

I had a miscarriage back in August of 2010, and didnt start trying to conceive again until just recently.

The fist day of my last menstural cycle was Dec. 22. I usually have a 28-29 day cycle. That would have put me roughly ovulating around the 4th of this month. Me and my boyfriend had unprotected sex the 26th,27th,28th, and 29th of Dec. I havent been experiencing much signs of pregnancy like I did on my last, but over the past week I have noticed alot more clear, slippery discharge, which i thought could be because of ovulation. Over the past few days ive been having a funny feeling in my lower stomach, kind of like a tingling i guess you could say. Starting yesterday i began getting a brownish discharge, and today when i went to the bathroom, (TMI, sorry) when I wiped there was a dark brownish looking blood clot, probably about the size of your pinky fingernail. Could that be implantation bleeding? My period wouldnt be due until around the 20th or so of this month, so I dont think that was because I was starting my period. My boobs are just now barely getting sore.

Any thoughts would be appreciated.

Thanks!