Difference between spotting and periods.

Hi I was under normal fertility treatment last month taking pills and injection to get the egg ruptured and later I was prescribed to take Susten 400 daily twice for 16 days vaginally. On the 17th day (04/17/2019) we took urine pregnancy test at home and the result was negative but I was having mild cramping and spotting just before 2 days we took the test and it is still continuing. We consulted the doctor and the doctor informed us to ignore this as this cannot be considered as periods and asked us to wait till I get my normal periods but I couldn't differentiate if this is my actual periods or just the spotting as doctor told. Please advise me on this as if this just spotting, what is the reason for this continue till now and when will it stop also will I get my periods post this. Please help on this.