I think i still have feelings for my ex!!!

Ok here's the story, about 3 yeaars ago now I was dating this guy, we had such good times, he always did things with, me included me in everything, put up with me, and in the end after 9 or 10 months we broke up ,mainly because I didn't know what I wanted! After we broke up I met my recent partner J now we've been together for 2 years and 3 months now, we've had a crazy Rocky rollercoaster relationship! Been through he'll and back! I love him so much but about 5 months a go we broke up for like 2/3 days I ended up going to my cousin and his girlfriends place , I stayed there a night, then I ended texting my ex he came and picked me up and went to his house, I stayed there the night, we had a few drinks with him an his mates , he was so so clingy to me it wasn't funny , (we had been texting for about 1.5 months before this an he ways saying how much he missed me) and I promised myself nothing was to happen! But it did, but I stoped it because I knew I still love j and I will go back to him once we sort everything out! The next day my ex dropped me home and my boyfriend wasn't home he went out camping , the next day my boyfriend got home, I didn't tell him what happened, things seemed funny between us and like nothing had changed! Anyway a week later my ex was texting me again, so we kept texting up until about 5/6 days ago when he told me that he has a gf and couldn't talk to me anymore I tested him tonight saying just hi how's things, he said shot I have to go away for few months for work,,,,,

But I'll be back, when I saw that I felt a bit upset! I love j to bits I truly do but what is wrong with me? Do I have feelings for my ex? Am I crazy what do I do????!!! I'm so confused! :'(