My friend with benefits..He gets jealous & mad if I'm talking to other men..Do you think he wants more?

I want to know...why do men get jealous..Does it mean he has to care more about me then he's willing to admit? or could it be he wants to be free but wants me all to himself?

He is 44 years old & I am 36 years old..We have been friends with benefits on & off again for 4 years. He gets jealous & mad If we are together & another man calls me or in the past I was open with who else I was seeing, he would get mad & jealous. He would show it by basically telling me I had to leave...then he would ignore me for 2 or 3 weeks...If we were chatting online on yahoo and I mentioned a man, then he would just sign off WITH OUT saying good bye & then also ignore me for a few weeks.

He has from time to time..told me he loves me & he wants a relationship with me...and I said yes (about 4 times) but he always ended up saying he changed his mind...but yet he still gets mad if he hears of another man.

I need more opinions please!