Do I have a speech impediment?

When i talk to people my words come out jumbled and barely comprehensible. Plenty of ppl will ask me" what did u say?!!" When im by myself im fine. This is embarrassing and looks bad on interviews too. Im smart, a great writer, but when i speak to ppl, it sounds like i have no idea what im trying to say and like im trying to "sound" smart even if i know everything about the topic. It feels to me like my teeth are pushed to inwards and my tongue doesnt have a lot of room to move around. My upper teeth do cave in towards the sides by the way and i have an overbite so my tongue has to reach far out when im trying to forms words that require the tongue to touch the upper teeth because they're are pushed far out from the overbite. I think its a nervous thing to. I cant get my words straight and/or when i say them even when speaking up and clearly, ppl STILL cant understand me!!