You told him no and he's still coming back. So either you're giving him mixed messages or he's not respecting your boundaries.

If you don't plan on marrying him then I'd block him. The worst that could happen if you don't is find out you're pregnant.. and he's changed his mind again.

I'm not sure there's sparks or if you're liking the fact that he's "wanting" you after he broke your heart. I've been in a similar situation (20yrs ago) and it turned out the guy wasn't interested in a serious relationship with me.. just sex. Umm, why bother? There's many fish in the sea, gawd. So luckily for me, I said no thanks and moved on without regrets. He broke my heart once.. not twice. Trust me.