People who make rude comments are ignorant. Making rude comments within ear shot is a way of giving us big hints that we smell and need to shower. They don't know that there are medical conditions out there that make people smell. Heck, most the medical community doesn't even know they exist and brush us off with, "I don't smell anything." even though they do.
If your mom and brother have commented about your odor, then talk to your mom candidly. Tell her this has been going on for the past 7 yrs. and even though you shower and brush your teeth every day, you still smell. Maybe she can help you find a doctor who can try to figure out what's wrong with you.
As for the young professors talking about you, this is so unprofessional. Talk to them after class or set up and appointment to talk to them. Tell them it's a medical condition that you're trying to get to the bottom of. This will hopefully stop them from adding fuel to the fire.