Need advice

Hi!! Okay so my last period was March 28th this is may 15th didn’t have a period and still haven’t had one. I was testing positive and the positives turned faint. Okay anyways no bleeding or cramping. I have a blood test Monday. Is it possible to be pregnant and never revive a actual positive pregnancy test?? Like I have two kids already okay I’ve NEVER missed a whole month of a period, and now we’re in the middle of this month and nothing still... like what the heck! Pictures of tests. And yes they all were taken within the time frame!