I do gym,but I do not gain muscle,i gain veins,my veins pop out,why is that?

[fede_gianga]

the only resultas of gym is the veins... I dont know why is that
I bought a multi gym in my house,I used it 1 month (likee 2 years ago).I only noticed that I gained more triceps
last year i went to the gym like 5 months and I obtained veins.
a few months ago I bought some things to do gym... I feel that muscles are working
I am a little bit fat... I should have 5 or more kgs of fats... if you see me on the street you wont say THAT IS A FAT GUY,however I have fats.
I eat good. 80% good nutrition 20% not good food
I dont do any aerobic activity,running,jogin or something
I do full contact,I feel that my chest and
triceps get stronger...
I do 3 sets
1of 12 reps,then another of 10 another of 8
when i did excersise in the gym My personal trainer changed the excercises and days of rutines
however I did not see any results.
Maybe its a genetic problem, I also thought in horomns or mayybe testosterone

Well I eat well
I weight 70 kgs and I am like a 1,80 cms tall
I have quiet fat in the stomach
and I do not know why I dont get muscles

Thank for your hel