Feeling Like the Third Wheel

Sometimes when I'm with my husband and his friends, I feel like the third wheel. They have their inside jokes and mutual friends and a language and culture (literally) all their own. They try to include me, but I am always one step behind. This makes me mad, even if I know they don't mean to leave me out. I feel awkward and a bit lonely whenever I find myself in these situations. I think that's why married people need to have their own friends and spend some time alone with their friends without their husband or wife. The next time I am feeling like the third wheel, I'm either going to grab a magazine and give myself a spa day or call up one of my friends to make a play date. There's only one kink in my plan. I'm fine with giving my husband his space with his guy friends, but I'm not so thrilled about leaving him alone with his female friends. What do you think?