IS he lying?

[WildWildWest]

Ok so I heard that the guy I been kinda seeing the past months has a girl that is interested in him or he is "doing" I heard this from my bro who heard it from another co worker (we all work together) the guy he heard it from isnt sure.. but he thinks that... him talkin to my bro in random convo cuz the guy who is friends with the guy I am seeing doesnt know anything bout me and him... so of course I get mad.. not even knowing if its true... he has told me several times that he isnt seeing anybody else but me... so of course I decide to question him bout it.. but I tell him I heard it from someone else not from anybody at the job, cuz I dont wanna get my bro or anybody else involved... so I tell him that I heard he has another gf, or he is doing someone else... he looked puzzled and was shocked that I guess had mentioned it... he said I must of heard wrong, that it wasnt him that person was talkin bout.. he said 'yeah im doing u" and I said "thats the problem, u aint been doin me, so maybe u r doin someone else" we havent spent time together in months... mainly my fault cuz of my busy schedule... so he after he leaves work he txts me and we discuss it further... but I then tell him he aint been doing me so he gotta be doin someone else... then he blows up! and tells me that I act like he gotta be ****in everyday, that I can believe what the hell I want that I am the last person he been with and he would tell me if he was doin someone else cuz he would tell me he wouldnt wanna deal with me anymore... idk what to believe now cuz usually when ppl get mad they are lying right? I mean we are not in a commited relationship but we have both told each other several times we aint seeing anybody else... Is he lying or telling the truth :/