Husband and I fighting a lot

We argue a lot. I am so mean to him sometimes but he is so thick! It takes him forever to understand things or make connections. I am a teacher so I am patient with students who have learning needs but when I deal with my hubby, I lose it. I have actually called him: thick, idiot, stupid, slow etc... to his face numerous times. I know it's verbal abuse and he is a nice guy who doesn't deserve it. You'll probably ask why did I marry him? Well, I was in love and blind. I honestly didn't notice it until later. I don't want to keep berating him and I don't want to lose him but how do I keep my cool when he's so slow sometimes? I catch myself praying that our children have my intelligence, or at least my quick wit. He's obviously got his talents and strengths but over-all he is definitely suffering from learning needs. His sisters and dad are quick. His mom passed many years ago so I don't know about her. The worst part is when others notice in conversation and I feel embarrassed. I pretend I don't notice but deep down I am so pissed off at him. How can he help it? But how can I also? I don't even know why I'm posting. I just need to vent and I'm hoping I'm not the only one with this issue. Please advise. I don't want my marriage to end but I am at the end of my wits. Please do not be rude! I already had one biatch leave a rude comment which I reported and hid. I am already down, don't kick me.