You're asking us if you should get pregnant against your husband's wishes and lie to him about how it happened. You're hoping that he will be happy about the pregnancy and involved and unresentful as a father. You're hoping he will share in the work....
It's not a matter of it being fair of him getting your hopes up. He is having second thoughts. What's fair is that he should be able to think this through. Having a baby, as you probably remember, is a big deal. An unbelievably huge responsibility. Take his concerns seriously. If you want this to go well for you, let alone for any potential baby, go to counseling together for some perspective and input from an objective 3rd party and decide the future shape of your family together. Respecting each other's concerns, desires and needs.
Considering that you are even thinking about getting pregnant without your husband's consent and then lying to him about it, I think marital counseling is an especially good idea at this point. Get yourselves rock solid as a couple. Then think about whether you want to add a new family member to the mix.