What causes a guy to stop liking you?

I started talking to this guy at first he would text me a lot. and was sweet... he wanted me to work with him... the job sounded good and it was a company I wanted to work at prior so I did... then I started becoming friends with people at work and he got mad about that.. like I flirted to much... so he stopped talking to me and started sending me bitchy text like how are you and so and so doing? and he knew we weren't together. And he knew I liked him a lot. but at the same time before any of that happened he slowly stopped talking to me and I'm good at noticing that stuff. but he seemed like he was jealous that I talked to any one at work...But at the same time he wouldn't tell me what happened like what changed ect...( I think it was work or he found a new girl) I was talking to him one day and asked him if he met someone else he liked he said yea but she didn't like me back... so I sent him a text saying I liked you back just saying... so he replies someone else...( like I didn't know that? ) so I asked him why he stopped liking me and he said to many little things? but he didn't tell me like anything really about the little things...when I asked he ignored me... I still like him a lot...(probably shouldn't like him at all) ... but he text me and said we can still be friends I'll see about the flaws later?... Like right now I'm at a point in my life where I just want to find one guy and be with him, I'm talking to someone else... he is a nice guy and all except he dips tobacco, been to jail for major drug charges, and smokes cigarettes...(like he is trying to turn his life around but I can't see my self kissing him... because the other stuff grosses me out.) but he is so sweet and we are just like each other. every time we hang out we are cracking up the whole time. about random stuff like since the first time we met..like even when we went out to get desert we ate our cupcakes like little kids in this fancy restaurant like swallowed them whole and it wasn't awkward. just like we have been best friends our whole life and we just met each other through acquaintances... I didn't feel like I was trying to impress him but he has already mentioned wanting to be in a relationship with me...ect... but the guy before is always on my mind even thought he doesn't want a relationship with me right now...like I really want to be with the first guy I started talking to but I'm getting mixed feelings about what he wants like does it seem like he wants me just as a "back up" and I'm giving him that opportunity. or should I just try to work out the issues with the other guy smoking and dip... I really don't like kissing guys that do tabacco it grosses me out... but in the same note he is very sweet... but I feel like I'd hurt him by not being "intimate" >>with him if we are together long enough... the thought of kissing him grosses me out (he has good teeth but I've kissed a smoker before and I just wanted to puke.
What causes a guy to stop liking you?
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