About A Year Ago I Noticed 2 Large Bumps On

About a year ago I noticed 2 large bumps on both sides of the anus that appear only when I go to the bathroom. I strain all the time, even though a majority of the time I have ideal snake like stool. I get a lot of gas and also have stomach groans and pains. My stool is normal but seems thin. When I push I feel like my anus gets tighter. I west to a gastro who went up there and said she couldn't feel any hemmorhoids and gave me bulking antibiotic which made my stools larger but made my stomach hurt. Now I am off of that and it went back to soft and smooth but I still need to strain still have the bumps. I'm afraid its not hemmorhoids because the Dr could feel any. Is this normal? Could it be that my anus is very tight?