No Period going on 3 months.

I'm so confused! I have 2 babies already, 2 1/2 & 1. I'm trying to conceive again. My last period was June 24th & ended the 29th. Not a sign of blood since then & today is September 5th. I've been testing & nothing. clear blue, first response, dollar tree, Wal-Mart brand.. although in July i did get some faint lines hours after taking the tests. But it's back to complete negatives. what's going on with me??? I have always had regular cycles until after having my 1 year old. I had her in August 2016. Got my period again in October, skipped November, had it every month until April. again in May & June & that was it.