I agree with the others, and would suggest you go online to clothing websites for tactile defensiveness. There are many companies who offer extremely soft, seamless and tagless clothes and socks. What has worked for some (surprisingly!) is uniformly tight clothing, like bicycle shorts and underarmour shirts that hold the child snugly. If you have a sporting goods store you could go try on some of those things and see how she reacts.
Because of her experience, Specialmom is our sensory expert. And, she has a ton of experiences that she could share. But, she would have to write a book to do so because you really are at the starting gate. Getting to an OT is super important! There are resources on the internet that can give you more information. The best I have found is here - https://www.sensory-processing-disorder.com/
Its a site with a ton of information. You certainly want to check out "Getting a diagnosis" and "tactile defensiveness".
Oh, I am a bit surprised your child's pediatrician has not been more helpful. If for any reason he/she is reluctant to do a referral, try and find another one.
Best wishes and keep in touch to let us know how things are going.
Have you ever heard of tactile defensiveness? That is extreme sensitivity to various things that touch us. Like clothes. My son actually has this as well. He has sensory integration disorder. Oh my gosh, socks and shirts can be a challenge! My honest feedback here is to look into sensory integration disorder and have her evaluated by an occupational therapist that specializes in it. We did the brushing protocol which really desensitized him. I can tell you how to do it but think it's best for you to see an OT for true help. At 4, other issues may be there but not showing clearly. Most doctors do not mind giving a referral to a specialist, what is to them? And an occupational therapist will guide you best. Now, I do think you may have to pay for part or all of the evaluation. I can't remember, but think I did. But it is worth it.
So, for clothing, we instituted rules. I first was careful what I purchased. Socks--- I found socks with no seams. We tried several until there was a kind he'd wear. Then I bought gobs of pairs. Luckily he liked an easy to purchase kind from Target more than the expensive ones sold online for sensory kids. He still, to this day, will NOT wear socks or anything on his feet at home. It can be 0 degrees out and he'll complain he has cold feet. But no, will not wear anything on the in the house. But we made a rule during the preschool years that when he left the house, he had to wear socks. It's a rule. He has to follow it. For shirts, he's super picky. No tags is obvious but the material also must be soft and the sleeve and neck must be in the exact right place. I've wasted money on clothes he WILL NOT wear. sigh. But I tried different materials and always wash wash wash until they are soft. And once I find something he likes, I buy more of the same. Pants have always been tricky, no jeans or rough/thick/hard material. He will wear athletic pants. Or shorts. But lots of sensory kids don't want anything on their skin or are the opposite and don't want their skin to see daylight.
But it really helped to make being naked (or shoeless, shirtless, etc.) not an option. The rule is you have to wear clothes. That's it. I know that seems like I'm just saying this---- but I instituted rules as the law and it is hard if they fight it. But you keep firm to the rule. She is taking clothes off, you are putting back on. Even if you have to dress her. And praising her when she will wear ANYTHING willingly.
My guess is that she does have other sensory issues that you are not currently aware of. There is also the social implication of this. If she takes her clothes off during a play date, she'll likely not be invited back. :>)
PS: my son is now 14. Still no socks in the house. But otherwise dressed at all times. :>)