Basically this, OP >>30067
Like others mentioned, sissies by nature are very secretive and elusive in their act. Even if you know he's a crossdresser, from his standpoint, at most you only know or have suspicions now. The next step is actually confirming and moving your relationship to the next level.
It's illogical from his perspective to suddenly think now that you're attracted to him in a sexual / romantic way, simply because you saw lingerie in his laundry basket.
Next time you hang out, preferably when you're both drinking and hopefully your inhibitions are lowered, ask him if he is a crossdresser / sissy, and reaffirm that it's totally cool if he is. If he does come out of his shell and actually admit it to you (which is a huge deal for any sissy), you can then let him know that you're into it and he shouldn't be ashamed.
He might admit it to you, but also express that he's not into guys sexually or whatever. If that becomes the case, cool, at least now you know for sure and can move on.
Whatever happens, happens, but at least you'll know for sure where to stand in.