Help me please.

I had sex with my boyfriend on Tuesday of last week. We used a condom but it was too small so we decided to take it off because we couldn't tell if the "stuff" on it was from him or from me. My period was due the same week. It did come as expected but it was unusual. The first couple of days it was an extremely heavy flow and after those two days it was barely even there. Is this okay ?? Should I be concerned ? Can you be pregnant regardless of whether or not your period came?