Hello football player
So the smell has been around for 4 years you believe it could be tmau, maybe secondary tmau you can get tested through the mebo website, it's about $150 plus shipping and it takes about 4-5 weeks to get the result. If you do get tested positive you can try a low choline diet. You should try getting a colonoscopy as anal fissures, hemmorhoids, infections or inflammatory conditions could also cause a smell. There is a tmau protocol on the mebo website along with a low choline diet for your age and gender you can try:
*Sequestering of trimethylamine produced in the gut:
1. Activated Charcoal: 750mg twice daily for 10 days
2. Copper Chlorophyllin: 60mg three times/day after meals for 3 weeks
Enhancement of residual FMO3 enzyme activity: Supplements of riboflavin, a precursor of the FAD prosthetic group of FMOs, may help maximize residual FMO3 enzyme activity. RIBOFLAVIN (Vitamin B2) SUPPLEMENTS: 30-40 mg three to five times per day with food to enhance residual FMO3 enzyme activity
I've tried that and it doesnt work for me but it might work for you. You can also try devrom as it supposed to take away the smell from your stool. I've also been avoided in class and it's one of the worst feelings I've ever had that situation so I know how you feel plus it's embarrassing when someone asks what smells or makes a comment about it, especially when you cant even smell yourself. There are some products by klima deodorant for sweating all over the body i tried them and they didnt work for me but they have good reviews. I hope something from this helps you a little.

Also I forgot to mention on the mebo website forum i came across this undegarment called undertec that doesnt allow gas to pass through it or something like that for people with flatulence maybe it might work for other types of odors from there as well.