worried about baby's weight.

My daughter is currently 13 weeks old. When she was born, we had struggles with breastfeeding and she lost a pound in her first week. She was 6 lbs 3 oz at her smallest. It took her 3 weeks to regain her birth weight and was even hospitalized for "failure to thrive." 
Now she nurses much much better now (about 15 minutes every two hours during the day), and sleeps at least a 6 hour stretch at night. She's a happy baby and is hitting her milestones. But I am ALWAYS paranoid that she's too little and not gaining enough. I put her on the scale yesterday and she weighs 10 lbs 5.5 oz. I read somewhere that a 3 month old should weigh between 11-12 pounds and am worrying now. Does her weight seem okay for her age? Should I be worried?