I dont know where to begin...

So, my fiancé told me that my sex is boring and mechanical, and he doesnt want it anymore. Obviously im hurt, but more so that its true. Im a stay at home mom to a 13MO, and im 23 weeks preggo, also plus size. So i have a hard time doing certain positions etc. I dont ever feel pretty or sexy so my confidence is so low, im almost afraid of trying something new. Id get some lingerie, but that isnt his thing. Anyone have any suggestions? Im already sensitive to this topic so please be kind.