A visit to the doctor or telemedicine is really a good idea. Please do it. If you can't get an appointment right away here is a thing you could try- don't wash your penis with soap, just rinse it with warm water. Maybe the soap is irritating the secretory glands in your penis skin, causing aforementioned buildup.
Fluid under your foreskin? To clarify, do you have discharge that you notice? I'm thinking along the lines as smegma. Not uncommon at all. It's in fact considered normal. I think chlamydia discharge is cloudy and thick usually. And often drips besides building up. But you'll have to think if that would match up or not. I am more inclined to think smegma buildup. Important to note that chlamydia can create a discharge build up too so you can always test for that. Good to cover all bases. https://www.healthline.com/health/chlamydia-symptoms-in-men Smegma is often kind of thick too. But not always. Smegma is a build up of skin cells, oil secretions, and moisture. Because we don't know much from your description, can you see the doctor to determine? Don't be embarrassed. Your doctor doesn't care and then they can give you tips related to preventing this and how to clean it. Or if it is chlamydia, an antibiotic will clear it up. So, see your doctor.
Have you been tested for chlamydia? It can cause a discharge.