I Was Very Skinny(16.8 Bmi). I Started Going To The

I was very skinny(16.8 bmi). I started going to the gym and completely changed my diet(eating more & healthier) which resulted in gaining 13 kg(20.6 bmi) of lean mass in 1 year and a few months. Exactly 3 months ago I started having loose stools and gas, but never cramps or constipation. Is this IBS(or worse) or can this be something reversible caused by my sudden change of diet?