Is it Normal for my boyfriend to consider forcing me to have sex?

It's not normal. The fact he has said it aloud means he's escalated from thinking about it, to seeing how you react when he says it. Start thinking about how you'll react if he does it. That seems the next step in his progression here. Why the hell are you offering explanations or having conversations with him to justify why you don't want to have sex? If you don't, you don't. It's that simple. The man has two hands - you are not his pumping station. I have a suspicion you know this guy is capable of doing exactly what you fear which is why your anxiety is on high alert. It's called a survival instinct. Have some respect for yourself and dump this loser.