If you keep finding it hard to put on size or you put on some size
and lost it even doe your training and diet hasnt changed??

Well then thats your problem you havent changed your diet
or your workouts. So many of guys in the guy and on fourms
asking for help simple change your diet on dont count on
supplements for everything.

Why have i stopped gaining weight or im loseing weight??
Lets start with the diet and lets you put some size on and
are now loseing that size well its going to from not enough
Kcals and proteins you problem wherent getting enough in
when u put some size on but your body took the proteins
from your blood! The proteins in your blood is usely called
"the free pool" your body keeps proteins in your blood and
is always useing and replaceing 24/7 if your not getting enough
proteins in your body will use its free pool to help its self
to repair and now you dont have enough proteins in your
blood and from your diet so your body is atrophying.
Samething applys to energy your body stores carbs and fats
that arent needed as fat in the body to be used as energy
later when needed if your a hardgainer or skinny u prob dont have
to much fat.
IF your taking in 2000kcals your prob not going to grow
you might shrink so lets start taking in around 2700kcals
a day on a bulking diet and in a breakdown of 250grms of
protein 300grms of carbs and 60grms of fats you should work up to that in about 250kcals interval untill you start to gain some weight
if you gain to much fat just cut back a bit till you find your sweet stop
so to speak. (remember this is an example of how to do things)
Dont shy away from fats they are your best freind they
are rich in kcals, a great form of energy, will help with brain power
help coat nerves and increase electrical conductivity in nerves.
Make sure they are healthy fats from the likes of fish, nuts,
natural peanut butter, coconut oils, lean meats, olive oils.

Get your proteins from lean meats (turkey, chicken, fish ect..)

Now lets get the carbs down carbs can be a make or break
the carbs you want are the kinds from whole meal dense breads,
oats, whole grain rice and pasta, some people can get away with
white rice. Since carbs are the main source of energy for the body
the longer they take to burn the better you wont get a huge insulin spike
then crash and feel crap and hungry like you would from eating sugar
foods like sweets and drinks. Get your carbs from what i i suggested.

Veg try and get some veg into your body as they will help transport
your cabs, fats and proteins around your body also a great source of
fiber take small amounts to avoid bloat and gas.

Supplements. If you are going to take any start with the very basic
multivitamins will help to improve how you feel and how your body will
feel (in my opinion) Also a whey protein is great just after a workout
and at night if i take it at night id take it with some milk you will recover
fast (at lest i do) a better option would be a casein protein either
from a supplement or a good low carb and fat cheese.

Thank you all for reading hope this will help you out this is all from my own
experience helping some people out im not a hardgainer my self but my tips have helped others and a bit of reading i am not
a doctor of any kind im just a guy who wants to grow just like you.
I will also be posting this up on other fourms so if your going to post this
give credit where its due