Is this classed as cheating? I feel so guilty! What do I do?

An ex work colleague got in contact a few months ago we spoke on snapchat then he asked for my number as he had a new phone & no longer had my number so we've whatsapped since then also we've spoken when we've bumped into each other out. When we worked together I quite liked him he's got a nice personality, I found him physically attractive & we got on really well. We worked most days together with 2 men & we always got told we were flirting we both dismissed it & he never found out I liked him. We have been speaking on a daily basis for a while now & he asked me for a nude photo, I said no but we carried on speaking I later found out that night he was out in the pub when he sent it a friend had seen him there so I put it down to the drink! A couple of weeks ago he ignored me that lasted about a week in that week my friend that had seen him on a night out had seen him out again & he said the guy I like had given him a dirty look which didn't sound like him which is what my friend said he said that Tom the guy I like had seen us shopping together so maybe he thought that we were dating & he liked me seen as we'd been speaking a lot. About a week later he started speaking & we were speaking normal again daily he asked me for a nude again, I didn't but I said to him I'm not sure I know we wouldn't be hurting anybody but I wasn't sure he was fine with that we continued speaking then he sent a photo of his privates we laughed about it we spoke later that night & spoke since. This morning a lady I work with said Tom's mum was in saying to her he was with this girl but he's thinking of breaking up with her because she's asking him to buy her lots of things & she's refusing to get a job. Is him sending that him cheating on her? I had no idea he had a girlfriend, I don't know who she is just that she's called Jess he's single on Facebook. Do I let him know that I know? The trouble is I feel so guilty but I still like him! What do I do?
Is this classed as cheating? I feel so guilty! What do I do?
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