Cheapies vs. FRER

So I took my 1st two tests with FRER and the lines came out almost immediately. I took an 88cent cheapie from Walmart this morning (the purple and white test) and the line was light. Just took the pink cheapie (bottom) and line is still light. Is it because they're not as sensitive as the FRER? I'm measuring 3 weeks 3 or 4 days. Missed period is scheduled for this Wednesday and I still have had sore boobs, and now nipple sensitivity. Some light brown spotting since Saturday the 25th when I'm mostly active during the day (walking, etc). Help! Miscarried in February after being almost 5 weeks so im super nervous!