I had unprotected sex 2 weeks ago from yesterday. Three days after that I started what I thought was my period but it lasted 4 days and was kind of heavy but lighter than normal. I had no bloating or cramps which I normally do. I'm not supposed to start my period until tomorrow though. I'm having some signs of pregnancy, but I don't know if I could just be freaking myself out. Could I be pregnant?

Pregnancy is possible, but unlikely since you have started your period. Starting a day early is nothing, most women have an off month once in a while, many things can cause this, stress, weight loss, weight gain, illness, medication, exercise, etc. etc.

See how this period goes. If it's not normal for you, then wait and see what happens next month. If you miss your period, test using first morning urine.