I think i’m pregnant

Patient: I have resently had the depo injection on the 6th feb, it was 6 days through my period so i was advised to wait 7 days before having sex without other protection, my partner and i only waited 5, and i had been getting spotting and stomach pains 2 days later, we were concerened so i took a test but i was told that the hormones may effect the result, it came out negative.. the spotting has been getting worse, and this morning i had a very light period, and tonight i now have a lot of very dark brownish bleeding… could i have had an early misscarriage or could it be from the depo injection ?