Neg. HPT, late period but many odd symptoms

Hi, I have been on the pill for 4 years and always get my period on a wednesday night, thursday morning at the latest, with few PMS symptoms. It is like clockwork. However, 2 weeks ago I was on penicillin, which lowered the effectiveness of my oral contraceptive. I had sex the day after I was supposed to ovulate (not trying to get preg. so that was dumb).

A week later I started feeling hungry all the time, but also had heartburn (which I had only gotten once ever before then). I was eating frequently suddenly, but not a lot more than usual, just small snacks. But I just kept craving stuff (not just chocolate like before my period). Also I felt nauseated on and off throughout the day for about a week. My breasts were tender (again, rare for me), but only for about 3 days. This all happened last week.

This week I kept feeling sick and had heartburn and tender breasts. I also noticed a strong smell from "down there", not good but not bad either, along with a runny nose for like 3 days. My period was due wednesday night, but I only had one pink spot, and I just had not been feeling like myself for a week. Thursday morning I took 2 HPT's, both negative. Then Thursday late afternoon I thought I got my period, just brown blood. But it stopped. Friday it started again with what looked like an actual period, but I had the worst cramps ever (I don't normally get cramps for very long). I felt sick and nauseated for a few hours, then it went away. Now it's Sunday and my period still seems normal, just slightly lighter, and I don't have many symptoms anymore except a little nausea here and there.

I am wondering if it was just a really bad period for once in 4 years since I've been on the pill, or something else. The heartburn esp. concerns me since I never get it. I haven't "felt" pregnant since friday, but am going to the doctor asap to figure it out since I am usually pretty in tune with my body. Anyway just wanted to vent, and I will update this thread with DR results, in case anyone has similar symptoms.