Does He Just Want to "Conquer" Me?

I've known this Leo male since high school, but about a year and a half ago he started to show interest. I mean pretty much stalking my Instagram. He's very attractive to me so I gave in eventually to try and get to know him more. We began to message each other, and then we met up one night. We weren't intimate but we talked for hours. The chemistry was definitely there. And then a week later I find out that his high school sweetheart is 8 months pregnant... again (they have a 5 year old son together). When I confronted him about it he told me the truth, and told me he'd back off to respect my space and the mother of his child... but 3 months later and he's still been trying to reach out to me. He's so tempting but are Leo's known to chase something they really have no intentions in carrying on? Any other man would've given up on me by now... or is it because he's really occupied with his children's mother and so the idea of another woman is exciting? I'm thinking everything...

I think you're missing the point and obvious red flag here. This is less of a Leo issue and more of a concern regarding responsibility (to your emotions and the emotions of his family). If his high school sweetheart is 8 months pregnant, it's safe to assume that she's very much still in his life (especially since they already have a 5 year old together).

He is obviously preoccupied and possibly looking for something else exciting on the side (namely you). Seeing that he wasn't upfront with you about the fact that he's about to have a second child with this other woman, there's no reason to assume that you'd be anything more than the side woman. I wouldn't recommend that you pursue this since everything is a bit too fresh. Tempting as he may be, you have no idea if you're the only one he's pursuing.