I'm 5'11 and a half/6 foot. I weigh 68.5 kg. I'm 30 years old. I play a lot of sport. Go gym around 1-2 times a week (pre-Covid) and eat reasonably well/fairly balanced meals. Any advice on how to gain weight/mass, without taking any weight gain protein shakes (messes up my stomach as I have IBS). Ideally want to get to around 75 kg asap.