No period while breastfeeding and possible pregnancy

So I have had my period again since giving birth in January. I’ve been ebf my baby girl. We have had sex multiple times, but I’m not sure when to test. I have tested over the last few days, but my tests could be evap lines? I’m so confused. They don’t seem to be getting darker, but I’m not sure. Top one is yesterday, bottom is today both fmu. I tried using FRER but they are so light that they could be indent lines which is why I’m asking about these ones.