Can't seem to progressively overload

Hi Marc,

I've been training consistently for 2 1/2 to 3 years and I haven't been able to increase the weight I use to progressively overload for a while now, so my gains have stalled.  I'm a smaller guy (5' 8" at 142 lbs) and I only manage to bench 145 lbs and squat 180 lbs for 6 reps.  I workout at home, so I don't have a spotter or a full cage with pins if I fail, making it difficult to train beyond failure.  I've tried drop sets and things like that, but I still can't increase me weight.  Any thoughts or ideas?

Thanks for you time.