Skinny to Strong

So I went to the gym with a co-worker who has not been doing workouts for a long time. We both used to workout together about 8 months ago. And then he stopped coming. I continued working out. After all this while he came to the gym and was pleasantly surprised with how much progress I made. He said "you really bulked up well and became very strong from the last time I remembered". He was the same guy who used to say I lift the "ladies weights". It is a great feeling coming from him. I still cannot compete with him in many exercises especially bench press and rows. Because I don't weigh as much as him and more weight - fat = more muscle and even after factoring out my relatively low body fat, I cannot match his muscle mass. I am equal to his strength when it comes to body weight exercises like pull-ups and dips. I still have to gain a ton of weight before I can make any big claims and gaining weight is the toughest thing for me. But for now, I am glad people...