I've been working out for three years now and i weigh 141 and i'm 20 years old. i wanted to start on a ph but i wasn't sure if i am still too young to start any supplements like thgat? any advice would be great.
Listen to Chub and the guys who are telling you to WAIT!!!
Regardless of your age (and anything YOUNGER than 21 years is a straight out NO to using PH!) 141lb is FAR from anywhere near the weight anyone who might consider taking a PH should be. Maximize yourself NATURALLY before going the hormonal route. And it can EASILY be done if you listen to the recommendations you are being given!
FOOD (eating LOTS of it), the right type of training (the big lifts, as mentioned, and following an appropriate split with the right sets/reps/recovery), the necessary recovery days, and the basic staples, are ALL you need to GAIN WEIGHT.
If you've plateaued, then you need to start either:
a. Eating MORE (and if you can't get the calories you need from all clean, high-density foods, then 'cheat' food is not really going to be an issue to eat of you have to get the calories in); or
b. Change your training regime around (and you should do this every 4-6 weeks, so that your body doesn't get used to what you're doing and top adapting).