First of all, you need to give yourself permission to be human.
Second, I'd like you to line up all the 18 month olds who brush their teeth regularly. It's going to be a short line!
Third, a lot of kids at that age don't speak much. Please take not of everything else he IS doing. Mine didn't talk much but he was walking very early, climbing, exploring, doing gross motor and fine more skills, and much more. He just didn't talk. When he started, he never stopped. If he's not delayed in other areas, he's fine. I found that, when I stopped meeting all his needs by speaking for him, he picked up the pace a bit, but that's all.
Your husband is stressing you out? Please take a weekend and go visit your mother, your sister, your college roommate, or anyone else you know (or find a hotel where you know no one), and let your husband manage for 48 hours and be the perfect, development-encouraging parent he thinks he admires.
What in the world does your husband expect? Does he think your child doesn't speak because you two aren't doing enough? Is he measuring against someone else's kids or someone else's pronouncements of what you should be doing? You two are doomed to a life of misery if so, and you will miss every glorious moment and achievement your child exhibits because you're too busy looking for something else.
You're talking? Great. Are you reading? Do you get him to point? Don't fill in every word all the time - give him a chance to talk, but don't berate him or lament it if he doesn't. Do you go to the children's wing of the library? Do you play in the bathtub? If you can't get on the floor right now, no problem - let him crawl up on the couch with you. Does he have a few toys in different categories - fine motor puzzles or shape sorters, gross motor kiddie cars or a chance to go outside now and then? Kiss him and love him - great. But there are other ways to show you love him, including giving him time to explore on his own. Do you play CDs or sing to him? Sing a song about brushing teeth, sing a song about bath time. Put a few simple toys in the bath with him - a funnel, a colander, a measuring cup. You don't need expensive stuff - just different shapes or functions. Do you have large paper and finger paints? Do you ever do simple cooking/stirring, kneading - VERY simple? Great.
Try not to push your child to meet milestones set by someone else, and try not to ignore great things he's doing in some categories by lamenting things he's not doing in other categories. And please go easy on yourself. You're doing fine, I'm sure, and you're tired and pregnant. Get some help from the dad who thinks you need to be doing more.