I had intercourse for the first time with my new boyfrined nov 27th 2010. I got my piriod that week. It lasted about 7 days. A week later I had symptoms like sore breast and cramping. I took a pregnancy test dec 25th 2010 and it was positive. Is it his? Or could it be possible it is my ex which I had not slept with in about month in a half

Since the time you slept with your ex, had your periods been on time and normal in duration/flow? It would be unusual to become pregnant days before a period starts, but not impossible. However, with the information you have provided, odds would be that your ex is the father.

You will have to wait until you have a scan done to get a better idea of how far into the pregnancy you are. A potential six weeks difference is far enough apart to give you a better idea of who the father is.