Help! dog peeing everywhere and I’m at my limit

Hi everyone, I’m really struggling and could use some advice.

My dog has started urinating all over the house, floors, corners, rugs, furniture, basically everywhere. It’s not just the occasional accident anymore, and I’m honestly overwhelmed.

We clean thoroughly, but it keeps happening. I'm thinking he is marking. I already taught him to pee on his pee pad. but still doing markings. The dog is normally sweet and well-behaved, which makes this even more confusing.

If you’ve dealt with this before, what actually helped? Training tips, health checks to ask the vet for, cleaning products, or management strategies, I’m open to anything at this point.

Thanks in advance for any guidance.