So. I've been dating for a while now (almost 8 months), and I really don't feel good with myself. I'm very insecure and my jealousy is kind of consuming us. I love her, but I simply can't think that I'm the one she really wants. Even though I try to hide this from her, I don't think I can do it for much longer... What should I do?

do what you think is right......like umm if you think she don't want you flat out ask her.(but brace for impact) she wants you she'll tell ya if she hesitates you'll know.
But I only wish luck to you to I was I was with someone..
But after 8 months maybe it's starting to dull a little try to act more umm exciteing? maybe

You aren't the only one she wants, period. It's a fact of life that everyone desires more. But, she's still dating you, so that should say something.

Frankly, you'll have to get over this if you hope to settle down or even become really good friends with anyone. No point in bringing it up, because there's nothing she can do about it. It's your problem that you have to deal with. I am right in the middle of doing that, so all I can say is good luck.