If what he said is true, what the hell are you thinking having another child?

I mean to be fair, it's not jealousy if he's pointed out anything that's accurate. If it's inaccurate you should assure him of that and assure them both that having a new sibling doesn't mean they mean any less or not enough. Sounds like he's concerned about finances and to a point that a fourteen year old might be ahead of his peers on. Trust me if he's already considering financial burdens he's probably scrutinizing himself harshly about them as well and that can mess you up at that age. Especially if you wind up with a surprise genetic disease that only amplifies your anxiety about that stuff.