Why do i always do this

I literally meet a guy I like. Talk to him day in and day out and start getting infatuated with him. Have sex with him, start to fall for him even more, then after having sex and talking for months I get bored and we quit talking then it happens to the next guy. I've only ever been in love 2x and I always get these strong emotions towards people I have sex with or talk to on a daily basis. What do I do? I fall too easily for people I just met.