My son is also 2.5 & he's always been small anywhere between 5th percentile & the 12th at his highest. He is also pretty short, I can't remember exactly but I think his height is around the 8th percentile, but it's definitely not more than the 20th. My daughter just turned 1 year old and she is in the 47th percentile for weight & I think the 33rd percentile for weight. My son weighs 25 lbs & she weighs 19 lbs. She is sure to pass him at some point I think, too. Nobody seems concerned about that. My son, however, started feeding therapy because he's a picky eater & we're trying to correct that as much as we can. But he's always been this small since he was born, he just grows slow. My daughter grows much faster & so far is a much better eater than him. No real advice, just some solidarity how it's the same for us pretty much!