Trouble increasing biceps curl weight

Hi!

I'm doing dumbbells.

I've been lifting for 2 weeks, but have done weight lifting in the past. Now, in the past, my methods were a certain weight, 3 sets, 10 reps. When I was able, I would go up to 3 sets/10 reps of the next weight up. I only stuck it out for several months those times in the past and never saw much progress in my look. I'm hoping to stick to it longer now.

However, I am now trying a new method of heavy lifting to build a little muscle and help burn fat for definition. I'm basically doing 2 sets of one weight, 10 reps, then go up to the next weight for 1 set, as many reps as I can (usually 4-6 reps). The next lift day I try to do all 3 sets at the new weight, 6-8 reps. So far, in the last 2 weeks I have been able to progress up one weight (5 pounds more) in every exercise except for biceps curls. I've had this problem in the past as well, every muscle group progressing except for biceps.

I"m doing 2 sets/10 reps on 15 pounds, and trying my hardest to just do a max of 20 pounds 1 rep on the 3rd set. That's all I can do, and I can only do that on the right hand and not the left. Any suggestions on how to move up to 20 pounds, 3 sets of 8 (then eventually 10 reps)? Am I too impatient? I realize 2 weeks is practically nothing, it's just frustrating that I've moved up a weight in every other muscle, and had this problem in the past.