I have question about my biceps. I am a Lefty. how come my left bicep kind of falls inward like a slump when I don't flex it and feels kinds of flabby and until I make a fist. But on my right side which is non dominant the muscle seems stiff. It is really weird as I always heard your dominant hand side should be stronger. I also do 40 reps on the left and 30 on the right trying to fix it but I have seen no change. Both sides use 11lbs dumb dell and 3 to 4 sets.

Any ideas? or Fixes?

Thanks

For uneven arms, i suggest you do the same sets and reps for each arm, and ALWAYS start lead with what you consider your weaker arm, because you have more energy when you start and more concetration. Do these two things and over time (2 months it took me) your arms will even out. good luck

also 40 and 30 reps is too much reps and you won't be adding barely any size/strength to our arms. Lower the resp to 10 and lift heavier.

Are bicep curls the only exercise you do?
As mentioned by FG above, your rep range is too high for any real strength gain but also consider that bicep curls aren't going to create a large amount of muscle anyway. You need to start focusing more on compound lifts.

Read the weight lifting sticky for the best advice on building a new routine.

Hey I'm left handed too

Doing 40 and 30 reps isn't going to help you at all. Try more weight and 3 sets of 10 (3x10)