I don't know if my washing machine has a built in filter, if it does would a ditry filter cause my clothes to smell?

Not sure about the 'filter', but sometimes the clothes in my washer are sour when I go to take them out (even if they've only been done for like 15min) - I've found that if I put like a cup or so of white vinegar in with the wash (not exactly sure how much I use, I just pour around the washer once when the water is filling up -) it prevents / takes away any sour / mildewy odor.

I smell mildew, too! But it's not everyday. Just sometimes when I walk by the washer, and it's usually when I have no clothes in it, but maybe did laundry that morning. It's a 10 year old washer, and I've never done the white vinegar - I'll try it! :)

Try bleaching out washer and then leaving open when not in use. Put bleach in it and fill it and open lid to let it sit in washer for an hour or so. DrTom4444