Hello from JustAnswer.
While it is common for a pulled muscle to still be causing pain 10 days later, it is unusual for there to be a significant worsening of the pain 10 days later, unless there has been a second injury. It is true that a muscle that is already pulled would be more sensitive, so may become re-injured with actions that usually would not cause injury.
Another possibility would be if there is another issue that arises, such as inflammation of the tendon or knee. If there is swelling associated with the increase in pain, there also would be concern that there could be a blood clot forming in a vein, although this is not common after a pulled muscle.
Since the knee support is helping, it would suggest that this is likely more inflammatory.
Yes, it is fine to take Co-codamol with the ibuprofen. The ibuprofen would usually work better for inflammatory conditions, but the Co-codamol may do better at relieving the pain. The actual concern would be taking the Co-codamol when you have already taken paracetamol. It is OK to take the Co-codamol with the paracetemol, as long as you do not exceed the maximum recommended daily amount of paracetamol, which is 3000 mg per day.
If I can provide any additional information, please let me know.