I suppose it depends on the person and the situation. It depends on the reasons you rejected him in the first place, reasons you say you don't even know, which makes it a lot harder to figure out.
You remind me of my husband when we first started dating... the situation is different but the sentiment is similar: We weren't exclusive in the very beginning. When I asked him about a relationship, he said he didn't feel he was ready to be exclusive / committed with anyone (it had little to do with me, in this case, but just in general). Well, I was ready. So because we were not exclusive, and I wasn't at a place in my life where I wanted to put my life on hold for someone who wasn't on the same page as me... I started dating another guy (all non-exclusive, just a few dates and what not).
... and my husband got jealous. He told me point blank that he had become jealous, and that he felt silly for that because he was the one who denied the relationship and therefor he felt like he missed his chance with me. I told him I didn't "belong" to anyone right now, and he had all the chance in the world.
That's when we began an exclusive relationship. Realizing I was now about to be with someone else just.. made him realize what he wanted, I guess. It was strange, and it was not my intention to make it unfold like that (you have to understand that my husband is not the jealous type, which makes it all the more incredible that it happened), but it certainly all worked out for the best in the end.
Anyway: Only you can really determine what you are feeling really means. We can only guess.
But sometimes situations work out funny like that. Sometimes we don't appreciate what we had or could have had, until it is taken away from us. Usually though, is a rare opportunity to be able to reclaim it after you've already given it up.