If a guy resents you is it because he is insecure?

I got on great with a guy but within a week he started acting needy, doing/saying things to get my attention. Constantly needing my reurance about him. I thought he was a fun conident guy but in no time at all he turned nasty and resentful. Making remarks just to get a rise out of me. he said many times that i was out of his league and that he didn't deserve me one minute then the next minute he'd try to undermine me. I'm pursuing a PhD and I feel he may have been a bit intimidated even though i never spoke about my work, was polite, respectful and always paid my own way. Im hopeless at these things, are these signs a guy is immature with low self esteem and is insecure in my company?