In my dream I was trying to ask questions to some of the DC but it was like I was having trouble speaking clearly. I was struggling in the dream, like they were listening to me, but I had to keep repeating myself till they understood. I was speaking english, but like (no disrespect) but like someone mentally challenged. Does anyone know what this means?
In other parts of the dream I could speak ok though.
This is normal DC behaviour for me. It feels like “talking to a wall”. Often I get the impression that the person is too drunk to understand what I’m trying to say. It is also very common to have problems with my own voice. This is very frustrating. In my case, I know that the dreams come from bad memories of drunk people in my youth, but maybe this dream theme is more common than I thought?
maybe its also because IRL you dont like it when nobody is listening and you carried that in your dream. 
Thanks for your replies, um Lucid Me, you may be on to something there, it is really important to me that people believe me, not that they just humor me with an occasional “oh really”, but that they truely hear me. Lately, I am having trouble with people believing me about this whole LD stuff, it is really frustrating to experience something sooooo exciting and real, and no one to share it with. UGH! Thanks for your input!
I have had a lot of similar experience in lucids. Sometimes I feel drunk myself. Sometimes I can’t see. Sometimes I can’t speak. Sometimes I have no limbs. This only seems to happen in lucid dreams for me.
This happens to me, whatever language I use (French or English) but only if, when lucid, I directly address to the awareness behind the dream (or the dream itself).
Something keeps my jaws tight, my voice is distorted and I cannot articulate. This goes along with a huge energy field (that prevents me from freely moving and articulating). However, my questions have so far always been carried out to the dream. I think speaking is mimicking the waking reality, in dreams, only intention really counts. So if your intention is fully directed to your question, difficulties in speaking should not prevent the message from being “heard” or understood by the DCs or the dream itself. 
I usually can speak without problems, but I’ve noticed that if I try too hard, so to speak, then problems may appear. In other words, if I’ve came up with a specific question and kept practicing it for a few days during RC then it’s harder in a dream as well. Spontaneous speech is easier. Reminds me of practicing your order in a cafe while standing in line lol. I seem to remember from language psychology lessons that if you repeat a certain phrase over and over again it becomes inhibited, an effect that you can notice when saying tongue-twisters. It may have something to do with it.
I never experienced this problem, maybe a subconscious thing? The problem I encounter is making the dream appear vivid even after completely knowing that I’m dreaming along with stabilizing the dream. Anyway we’re all different so I’ll try to help you. In your next lucid dream, try clearing your throat before speaking also try drinking water and assume it’s clearing your throat. I read this at a forum at Dreamviews. Lastly, consider trying the tips the others give.
Well I have had this issue in lucid dreams. And I see that there are already many ideas thrown around in this thread as to why it happens, so I’ll offer my own too.
The lucid dream is a new environment for you and it’s intimidating you a bit. You don’t feel in control of it and you doubt that you will succeed in anything you do. You might feel undeserving of the wanted result, like it would be too easy.
So yeah, I’ve shouted in lucid dreams/non-lucid dreams and only a whisper came out. Sometimes opening a door is too much for me to handle. Flying was an issue in the beginning…I think it’s all because deep down you have doubts. Get rid of those and things will start to work in lucid dreams. In some lucid dreams I fear that the dream will end any second and I try to rush to my goal. This usually gets me nowhere. If I’m able to calm down, I’m able to take control of the situation and things start working.
PS. Also remember that you don’t have to open your mouth to speak in lucid dreams. The dream characters can hear your thoughts if you want.