Man of Honour
[..] so I had a cull and chucked them all out and replaced with all CK ones. But now I feel like if anyone see's me they'll think I always have the same pants on!
Unless you're an old-fashioned superhero who wears his underpants on the outside or you routinely walk around in public in just your underpants, how is that going to be a problem? Even if you do, I think almost everyone would notice either of those things a lot more than they'd notice details of exactly what underpants you're wearing. OMG, it's Superman! Again! But wait, what is this? His underpants look the same as last time!
If I was intimate enough with someone to often see what underpants they were wearing and their underpants always looked the same and they didn't smell, I would simply assume they have enough pairs of the same type of underpants. I think any rational person would, given that underpants are machine-made mass market items. If you have found a specific type that is comfortable for you, why not just buy a dozen of them and be done with it? The last time I bought socks for work, I bought 24 identical socks. Wash them, any one pairs with any other one. Job done.
I'm not seeing the problem here.