Since you are having bright red blood on the toilet tissue, this does sound like hemmorhoids which are caused by straining to have a BM or lifting heavy things. Preparation H has a product to reduce their size. IBS does not cause bleeding. Make sure you are drinking plenty of water, and if you have trouble having BM, think about using a stool softener. Fiber is good, but too much causes constipation, so just be careful. You may also want to add yogurt enriched with probiotics that aids in digestion.
Youth is on your side, and I think you can relax in knowing it's hemorrhoids which are benign, just bothersome. Take care
Ask your doc to give you a fecal blood stool test. You use it for about 3-5 days and wipe some of your stool on the chart....(sounds gross, but works) and then it goes to a lab for processing to see if anything more than hemorrhoids.
Also, a good way to relieve hemorrhoids is to use a "sitz bath" with epsom salts. These are available at most pharmacies for about $30 and you fill it with warm water with some epsom salts and place over the hopper to bathe your sore area. Twice a day for 20 minutes each works wonders!