Here are my observations about your question:
1. Your cycle was normal at 23 days like prior ones
2. Intercourse on 3/2 was day8, which is definitely a bit early for conception, regardless of the short cycle
3. You took the pregnancy
test early - it will typically not turn positive until about the day of your period at the earliest.
4. Some of your symptoms are consistent with pregnancy, but some are not ones we would see this early in a pregnancy (skin darkening around nipples)
5. It is not uncommon to have 'implantation
bleeding' around 4 weeks, about the time that you would get your 'next' period. This bleeding sounds heavier than that.
So yes, this might have represented a miscarriage
, but unlikely. What I would recommend is to repeat the pregnancy test now and again in a week. If you have an abnormal cycle again, contact your OB/GYN. I hope this helps.