Chemical pregnancy at 3 weeks

Suhaifa • Pregnant with Baby #2 | Attempting VBAC
Today I experienced a chemical pregnancy about 5 days after my period was due. I was around 3 weeks pregnant. I found out I was pregnant on Tuesday but HCG levels were not doubling and then decreased. 
Bleeding started yesterday but was light and progressed but not heavy at all. Still drops on a panty liner. Minor cramping as well.
Anyone experience the same thing? How do I start tracking my cycle again? Do I count this as a cycle or wait for AF to come? Does AF start now or next month when it was due?
Can you share your story and when you fell pregnant after your chemical?
Should I go see my doctor? He didn't say I should come in but is it necessary? Any advice would be great