If you don't feel comfortable sharing then don't. I don't think it makes you dishonest at all. Honestly they don't need to know unless it conflicts with required job duties.
You should tell them because if they find out from you showing they won't trust you. I got a job for being honest and tell them even though I went in and didn't look pregnant because of my choice in clothing. Always better to be honest
I would say definitely tell them. You're going to start showing soon and if u get the job u don't want to come across as dishonest. It's against the law for them to discriminate against u do to pregnancy. But it does happen :( so good luck and do what u feel is best for u