I am not a sex counselor or professional, but it sure sounds like he is obsessed with sex. Will you continue to tolerate/accept him?

Define normal. Perhaps your apetite's are different and you prefer different meals. That is okay. Normal is very subjective.
The question may be are you two suited to each other? I'm guessing by the title of your post that you are not.

I thought I was bad...

Actually, it seems normal that guys are interested in other women, even though they are in a relationship. It seems like a "instinctive" thing.

I think that as long as he shows primary interest in you, doesn't try to hit on other girls/women, then you know that he loves you still, and wouldn't do that sort of thing to hurt you.

There are guys that will dedicate themselves into a relationship, abandon any other sexual desires, or toys that they might have had before, but those are rare. I for one, cannot do that.

So is it "normal"? I would say yes and no. To women, this is not normal because it's not something that they do. To men, some would find it not normal, some would. I say that he should know where to draw the line.

Him getting an erection like that is a clear indication that he was turned on by the sight of another woman. Biologically, this is normal. In terms of a "relationship", this probably isn't a good thing. The question now rises, if you weren't there, would he have approaced her and tried to have sex with her?
If no, then your relationship is safe.
However, don't be paranoid and let your insecurities get in the way of your judgement, and your discussions with him about this issue.

See my post:
http://www.neotaku.com/phpBB2/viewtopic.php?t=6368&start=0&postdays=0&postord...