Ay nako, that sounds really uncomfortable talaga, may a few of us moms na nakaexperience ng ganyan, usually from sweat, friction, or sometimes yeast infection lalo na when pregnant kasi ang hormones. Since it's affecting your walking na and you're in pain, I'd really suggest calling your OB now instead of waiting til May 19 kasi they can check what's causing it and give you safe options right away, walang point na maghintay if you're struggling na. In the meantime, keep the area dry, loose cotton underwear lang, and avoid tight pants muna. Sending you comfort, mama!