I had a menstruation like coffee grounds and it did not come any more ...

I am 31 years old and I am married, in August I had menstruation like coffee grounds for 1 week that came and went, in the previous months my menstruation was regulated. I did not mense in September until today; I did a pharmacy test I gave negative, about 2 weeks ago and I'm getting fat and every now and then I have strong dizziness, my appointment is only at the end of next month what can I have?
Expert answer:

It may be pregnancy, some hormonal change, or other situation or illness that may be causing these symptoms (even emotional problems can cause this).