Should I be offended if family members know I am not religious yet mention religion constantly in every conversation?

No one NEEDS to bring up any opinion (whether it's about religion or not) in every conversation. That's inappropriate behavior. They are offending YOU. Call them on it. If they don't see how rude they are being, think about this option. Turn if around on them. Think of an opinion you hold (preferably something less emotional than religion) and mention it every time they mention religion. Turnabout is fair play.

I wouldn't be offended. If you are strong in your religious beliefs (even atheism is a religion), it becomes THE only way. It shows that your family has faith..Tell me, what would it feel like if they changed religions with the seasons and tried to convert you along for the ride every few months? Religion becomes lifestyle. In many places, bringing up religion can be inappropriate, but it's family, and in families, even the weirdest topics are fair game.

I don't call people out too often, but Oleg's post is one of the more ignorant that I have seen on any question. He's basically telling me to disassociate from my family because I am making an effort to better understand where they are coming from.

I think you should try your best not to be offended. They may be doing it because they think it will help you to find God again. Even though it's misguided and annoying, and you don't want to hear, it may actually be coming from a well intentioned desire to help you.

no you should not be offended when other people talk about religion

No, you have every right to question them about it if they bring it up