Had a hip replacement 10 days ago; now in pain even though walking, exercising. What do I do?

Of course contact your orthopedic doctor about this issue, but keep in mind that 10 days after having hip replacement surgery is not a long time at all. I had my hip replaced over 3 years ago, and I had quite a bit of pain for a long time, and still have some pain today. Not enough to stop me, but enough to be annoying. I discovered the year after my surgery,(from a CT scan)that my iliopsoas muscle(which is your main hip flexor muscle) was severely atrophied, so now I just contribute my pain to that.
Make sure that you're icing your hip regularly and not overdoing it. I hope you improve soon.

Call your doctor and ask. If the pain is severe right in the joint, it may be an infection that needs to be addressed immediately. If the pain is achy but improving, that is likely normal. A lot of stuff is trying to heal. Don’t overdo the walking and exercise. Physical therapy for hip replacements (anterior) is gentle and slow. Again, check your medical team. I had two hip replacements in my fifties.

First thing is to call your doctor.

You may not be taking enough pain meds. When my MIL had back surgery we were very concerned about addictive pain meds but the other concern is that if you don't mitigate the pain you won't do the PT vital to your rehab. If this is the issue, maybe see if a trusted relative or neighbor can be the one distributing your meds so that the addiction issue is at least on someone's radar. My very sweet MIL became addicted right under our noses. It can happen very sneakily and easily to anyone. But you do need to first figure out the reason for the pain and then to get the pain under control.

Some hip replacements contain cobalt and they've discovered that some people have a reaction to this -- pretty rare and unlikely -- but I would just ask this question to the surgeon, to be considered if you continue to have pain issues even after addressing all other probable causes. Wishing you a speedy and full recovery.

This should be discussed with the Doctor and the PT.
Unless the pain is excruciating I would think some pain is "normal" during the healing process. After all the bones were "broken" and they suffered trauma when cut and a "foreign body" shoved into the bone.

Is the person in question hiding their discomfort from their care team? I would discuss with them (OT/PT/RN/Physician) about pain control and things that need to be done to help alleviate it, as they are the subject matter experts. Hips and knees can tend to be painful rehabs.