Please help me.

The last time I had sex was Nov 11 but the time before that was Oct 31. We always use a condom periodically and we make sure that his penis doesnt go anywhere near me unprotected. On Nov 12 I started spotting and this kept on going on till now, Nov 17. I think it's implantation bleeding because it was really light but only got heavy for one day and became really light again which is not normal for me. I usually have a very heavy period. It also didnt help that my period came a bit too early. The last time I had my period was Oct 20-26.. I'm experiencing severe constipation for the past two days. Could I be pregnant? Please help!!!