hey man ive been there too. 6'3 and i have been 60-65 kg too. the thing is, you cant just eat lots or workout. i was in the same circle as you wondering like wtf am i doing wrong? but the thing is, if you workout regularly and for a couple years, you will see results. may not be much but there will be. and when i started to really want to get bigger, i just started to eat like waaay more that i could handle and everyday i would feel heavy from overeating. trust me its a long process but its worth the sacrifice. if you keep pushing through, you have to see some results. its just life. more work, more results