Why would he ignore me but gets jealous when I talk with other guys?

this guy I kind of like and hooked up with in the past recently started ignoring me every time he sees me, he won't make eye contact and would get all quiet and serious every time I come over, and it's not like I haven't tried talking to him but he just gives me really short answers and doesn't seem to want to have a conversation with me, but when he sees me talking to other guys he still looks upset and jealous. I'm so confused! Any help?