Depo and only one period

I got my last shot in August of last year. I didn’t get a period until last month, and it’s been 4 days and I’ve still not started my second period. Is this normal? I will add that me and my partner use protection every single time we have sex and so far (thankfully) it hasn’t broken or busted. I know some people get two periods off of depo and not a third one bc that’s what happened to me at one point, but I don’t know why I haven’t had a period this month.