You are getting some strangely condemnatory responses on here.
For example, I don't see how you acted "like a doormat" by having sex you wanted to have?
(I am assuming you wanted the sex - nothing you have said suggests you didn't).
You are fully entitled to have sex with any consenting adult you can find. You are not obliged to like every aspect of their behaviour before you do so.
If you thought "these questions about who I have been seeing are weird, and getting on my tits a bit, but I am still horny and fancy a shag with this willing, if annoying man" - that is very much your right! And anybody criticising you for it has a few hang ups of their own in my opinion....
You SHOULD be wary of any lasting involvement with him, I would argue, because he is demonstrating jealous/controlling tendencies that would be unpleasant in a partner and could even potentially lead to abusive behaviours.
And you WOULD benefit from clarifying in your own mind why it matters to you what his feelings for you are. Is it just curiosity? That little bit of revenge pride we can sometimes feel if an ex who dumped us then appears to want us back?
And of course, none of us actually have a clue how he feels. He may be entirely indifferent to you and just want sex. He may go to sleep every night sobbing into his pillow and murmuring your name. It is just not possible for us to know.
Your best chance of finding out is asking him. If you care enough.