How do I make my clothes not smell like B.O?

I'm a larger dude who has a certain set of clothes that I like wearing. Now I'm talking probably once a week (or less) I'm wearing certain t-shirts.

We use quick washes to do our clothes which is fine for my girlfriend's who doesn't sweat like I do but for mine it just doesn't seem to actually clean them rather just get dirt out?

Which setting should I be using? Or do I need to scrub the armpits or something like that to make them stop? And should I do that every time?

Help please! Alot of my favourite t-shirts are borderline becoming not wearable because of it.