What to do when being a friend to him is taken as interest?

There is someone I work with who I did have an idea had a bit of a crush on me but I didn't find any interest in him but there was one day a bunch of co workers got together for a birthday so the co worker with a crush , another co worker and I showed up together once it was the end of the night he dropped us off I was the last one and that is when he asked if I wanted to try to have something with him I was a bit caught off guard since this was our first time meeting/hanging so I nicely said that we don't know each other and to be friends

From there the three of us would continue to hang out however the one with the crush would always make it known and do nice things for me and from time to time the guy with the crush and I would hang out one on one cause initially I thought being friends and seeing where it goes was best but he never really treated me like a friend just like he was always trying to win me over.

Problems would always arise because we'd always get to the same bump in the road of him asking to try for a relationship and even things were said like I'm using him or want the girlfriend treatment when he would be pushy and insistent when doing or giving me things. I would tell him no but he would insist or at times get upset but not fully show it or say he was upset way later.

I treated and acted like a friend to him. The cause of the issues we would constantly have was him having these expectations and feelings that weren't being reciprocated so he felt he was chasing with no results because when he would ask and I'd say no again. I know I said being friends and getting to know each other was my intention but given the constant issues and one blow up on his end then later blaming depression and the constant egg shells I'd walk on with him I have no desire if I ever had any to date him cause its been too much on me emotionally. I know my problem is I've been too nice with trying to be friends when it only gave him the wrong impression

What to do when being a friend to him is taken as interest?
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