Weight lifting and boxing are two different sports, so if you only do one of them there is of course going to be a difference ya know. I am sure you are stronger, just in not the places you are wanting. When I use to just weight lift I was pretty swole (for my size ) but once I pretty much stopped all the weight lifting, yes, my upper body did seem to get smaller, but there is no way with the training I do now for boxing I would say I am weaker. But everybody is different though too.