Hi there!
A friend of mine, who started on Chaturbate not too long ago, had very similar questions. Those questions can be a bit daunting, especially since it may turn you away from what you want to do, but definitely do not allow that to happen. Once you have a better understanding of what you want, need, and are comfortable doing for others, it becomes a bit easier.
In terms of the site you want to use, I would recommend researching a few of them, such as MyFreeCams, Chaturbate, StreamMate, and so on. Researching these sites will allow you to get a brief understanding of how model to member interaction works, what the general viewer base is looking for, and what, if any, restrictions are in place for the different viewing methods. There are definitely a few sites to stay away from, but that would be determined based on what you feel most comfortable with.
Pregnancy is natural. Being able to get on web cam shows people that you are self confident, which plays a huge impact in your success. Personally, I like pregnant models. Others, may not like it as much. Everyone has their own likes and dislikes, but there will always be people who like who you are and what you do.
As long as you stay true to yourself, stay engaged with your viewers, and always know that you, just like everyone else is unique, you will do fine, and yes, make money!
It's ok to not know what to do, and that's why ACF is here!
Oh, and get verified once you have chosen a site!
https://www.ambercutie.com/forums/threads/how-to-get-model-status.1696/ - lots o' goodies for you if you do!