Ibs with minute hemmoroids. To me.

I have done colonoscopy, usb, hepatitis b,c and whole body test , I have to go to stool 4 times in a day. My stomach bloated after meal with gas. I have found blood in tissue paper after stool and one time during stool . I have lost 4 kg wt in past 8 month. According to dr I have ibs with little hemmoroids. I m clinically depressed from past one yr about my health. I want to gain weight. I m underweight since childhood. could I go for mass gainer with lactose free to gain weight or it will harmful to me. Plz suggest me . My height is 174cm and my wt is 58 kg. I will be very thankful to u. I m not able to find gud stomach doctor . I m suffering from past 1.6 yr and I haven't any pain in stomach till today.thanks