Ammonia smell on underwear

hi this has been going on for a while now and its driving me crazy i was tested for STDS had my smear test had urine sample taken for UTIS and all came back normal but there is an ammonia smell on my underwear and its worse if i wear underwear like things or brazilians my GP gave me antibiotis for BV but it didnt work there no itch or anything and there isnt any unusual discharge my underwear is only wet and can only see the diffrence in colour because its wet im not sexually active and been through BV antibiotics twice and nothing happened i was and clean i change underwear twice a day and i use wipes also does anyone had this before?

Try drinking more water per day and I bet that will clear it, you have ruled out anything that would require treatment so its pointing to a low form of dehydration, is you urine darker than normal, like a pale gold colour

i drink 3L of water daily

Then obviously not a form of dehydration, I suggest you ask your GP to do a range of blood tests to rule out other possible causes of ammonia smell like kidney /liver not processing waste correctly