Need some help

I got off the mirena IUD in February and had my period right a way and had it every month since. My period is regular and have never missed a month however it is longer now than it was before the iud(34/35 days). I started TTC AT the beginning of April. This month I think I ovulated later than the app I was using predicted, maybe 1-3 days later. I'm between 11-14 days dpo, got all BFN. Through out this cycle I've been really crampy with tons of back pain and have egg white discarge for a few days now (doesn't usually happen right before my period). My period is predicted to start today or tomorrow but out doesn't feel like it's gonna start. Usually a couple days before my period my breasts would be sore and would have cramps in lower abdomen and almost in my vagina (if that makes sense) but that isn't happening. Is it possible to be pregnant at this stage and still get a BFN? I'm using cheap strips I got from Amazon so I don't know if they might be faulty. I also don't know of things are different with people who have longer cycles. I'm 23 and new to all of this (trying for baby #1). I'm just looking for some advice or is there anyone in a similar situation or have been? Thanks in advance.