Ditto to asking your doctor - call in the morning. Three days late is not usually enough to cause heavy bleeding by itself - that does happen often when women are weeks late or if they have very long cycles anyway. But anyone can have a heavy period now and then. You don't say what "all the symptoms of being pregnant are" - there are so many! But if you have bloating and breast tenderness, for example, those are also common accompaniments to menstrual cycles. If you are nauseated, that can be as much due to heavier bleeding or something unrelated (like a tummy bug) as to pregnancy. I worked in women's health care for years and we saw symptoms like this all the time. Women vary, and individual periods of individual women can vary.
If you've been using contraception properly and effectively, there's a low likelihood that you are pregnant. But no method is foolproof, as you know, so you should always be prepared for the possibility and act accordingly in terms of alcohol consumption and so on.
If you think this heavy bleeding is due to a miscarriage (and I'm only guessing it's your concern because there is nothing in your symptoms per se that says "pregnant" in big bold letters), it's possible but not likely - even if you were pregnant, it's unlikely you would have that much bleeding just 2 weeks or so past ovulation, which is less than 2 weeks after implantation. So again, you talk to your doctor and decide together whether a blood test is indicated, or if you even need to be seen.
Please don't diagnose yourself over the internet, either through too much searching with "Dr. Google" or through too much surveying of women on line. A simple clinic visit or a test with your doctor will answer your question about pregnancy, and if necessary, you can be seen for a follow-up if this heavy bleeding recurs with future periods. It's great that you are keeping records of your periods, and do continue doing that (not just when they come, but how heavy/light/long-lasting they are).