As above, we did not pants for about 3 weeks until our little one got the hang of it then took him shopping and let him pick some! Pants are tight fitting like a nappy so it can be confusing for them this early on ☺️
You could try commando(loose pants, no underwear) but I he is still having issues, keep him bare bottomed for a while longer.
Knickers feel like a nappy so they do have more accidents cos once something is on them they think they can. Either go back to naked from the waist down or persevere