A muffled ear is an interesting problem that has several possible explanations. I recommend that you speak with your doctor
. The most common answer is that you have something in the external auditory canal, and the most common explanation for that is cerumen, or ear wax. Having that removed is a good first start, but it is not necessarily true that the wax won't come back. It's a good idea to have those checked regularly. The more interesting part of your question is that you note that your ear feels more muffled when you are standing. This suggests a positional element to your problem, and ear wax might or might not show up like that. Another idea would be to have some sort of problem with drainage from your ear. Your eustachian tube is responsible for draining the middle ear, and problems with draining from that tube can present as muffled hearing. In that sort of situation, there are a number of different explanations for why the tube isn't working well. Speaking with an ear nose and throat surgeon
(AKA ENT AKA otolaryngologist
) is one of the best ways to help clarify what is causing your actual problem. Please speak with your doctor about this.