You mentioned you were concerned about K-1 being more costly. The total cost of the K-1 vs the CR-1 journey includes much more than the application fees. It is extremely complex. The total cost could end up being 10's of thousands less expensive or it could be the opposite, more expensive. It all depends. For myself the K-1 was 10's of thousands more expensive due missing out on being able to file married-jointly earlier. But the K-1 saved me thousands in other ways to slighly offset the loss, but I still had a huge loss. It all depends on the couple/s personal situation and circumstances on whether the total cost will be less or more. But I don't care, because more importantly, I got what I wanted, which was being engaged and getting married in the USA with my family,
You also said your primary concern was having the baby born in the USA, and presumably to be living, staying, physically and mentally supported, with your husband during that time. Maybe he is concerned about bonding with you and the baby during that time, helpting you out, etc... It's very unlikely you will even come close to that goal with a K-1 or a CR-1. Hence, since you have been planning this wedding for a long time, and that is what you want, it seems reasonable not to delay that plan, especially since you are pregnant. But that is a personal choice. But first, I would suggest discussing your situation with a lawyer to see if there is any other way to achieve your goal without hurting your future immigration journey.