TMI Birth control shot has fucked me over x

Need some advice ladies,

Friday 22nd Feb I took the morning after pill. Today, after a night shift, I woke up around 12 to what can only be described as early labour pains. I am 100% not pregnant as I’ve done a test and Drs done a scan. But I had some thick brown discharge. I haven’t had a period since April due to being on the Depot. I feel like I’m dying. I’ve had 2 hours sleep. I’m at work with the worst cramp, no blood and some brown/blackish discharge. Is this a sign my period will be soon??? I feel like I could cry. Help x