I am being messed about what do I do???? xx?

I am 20 and I am called Alexia and two years ago I started fancying this guy who was 24 called Nick, who had started working in the super market that I went in every day. I found out he had a girl friend then a year later I got his mate (who I had become friends with) to ask Nick if I could have his number Nick said "Yeah sure" We were texting for ages and by the time summer came we were really close and he would come to mines and we were really good friends but we both liked each other and never said. Then we started "ting" and things started to change and in October last year we randomly stopped speaking and he wouldn't tell me why. I planned on never speaking to him again, 7 months had gone by and it was now May of this year and I had stopped going into the shop for the past 7 months to avoid seeing him, but then one day I decided to go in and he stopped me asked for my number and asked if I would go out for a drink with him, I thought I would be civil and let bygones be bygones and said yes. After that we became really flirty and started going on dates. Then one night he said that he and his friend John had a free house did me and my friend Abbey fancy going round. That Night I had with him. Then in the morning he told me he had a GF and that he had, had one for the past 5 months. I decided to stop talking to him again and 2 weeks later he called me and told me he had left his GF and he wanted to be with me and I had with him, again he told me the next morning that he was still with the girl and that they had never split up. I have been on a 3 week holiday and have been ill for a week so I haven't seen Nick in just about a month, 2 nights ago he text me for a chat and said he felt ugly (in my opinion he is gorgeous) and that he can't get girls anymore and I said "so . . . You have a GF?" and Nick said "No, she dumped me" and then we got onto the conversation of me maybe being his GF but to begin with just for fun (my idea) then yesterday I went on his FB and found out that they had never split up text him saying "Now I know you cheated on ur GF the last two times but this time you are single?" I never got a reply! Why do you think he keeps lying to me???? Does he like me but it's just the wrong time or is he using me? I am so confused what should I do? xxx