You should try tracking your macros (this is the most important) and calories intake, there are several apps for that. If you are undereating you will most def not be able to build muscle and grow strength.
Not enough information to really say. Lifting is a fairly general term and can represent a number of various resistance training programs with different goals.
You mentioned strength so I would ask are you in a strength training program? What lifting program do your peers use?
I started training my sons strictly with compound lifting around age 14 and as they became competent with their techniques they followed a strength training program. They regularly tracked their 1RM lifts as well as their measurements and food intake. So there was a clear measure of progress throughout the years.
As far as nutrition, do you have a baseline of what your body requires to gain strength and do you track it? If you are an active teenager it could be pretty high.
My kids were dual sport athletes and consumed around 3200 to 3600 calories a day.
As I said, there isn’t enough info to really comment on your issue but I would recommend that you establish a strength training program if your goal is to gain strength. Baseline your nutritional requirements for gaining mass and consistently track your nutritional intake.
As long as you’re eating a good amount of calories & getting your protein in you should be building muscle. And yes if they started their journey before you they’ll have bigger muscles just like anyone in the gym who has lifted for 4 years vs 1.