Guy friend giving me mixed signals?

I have been with my boyfriend for the past three years. Recently I have noticed that his cousin, (one of our really good friends) have been secretly flirting with me. He always gives me eye contact and doesn’t break it after a few seconds, I catch him staring me whenever my boyfriend isn’t looking, he always gives me cute little smiles, but only when no one is looking. He always picks at me and bakes my favourite treats whenever we all hang out. We are all close enough to make dirty jokes about each other and laugh it off, but whenever he says something dirty and I go along with it, he drops everything and forgets he said it. I don’t know if he’s seriously or because my boyfriend is there? For instance, I was telling them I had my own porn website as a joke, and he told me if I did, he would never look at it. He never told me why? Is it because my boyfriend was there not even paying attention, would he really not look at me? One day while fixing pipes in his friends house, he asked me if I had ever done anything with pipes and I said do I look like someone who would? (being a girl :P ) and he said I dont’ know, I’ve seen a lot of hot girls in tradeschool doing it. I’m really confused and I don’t know if he likes me, or I’m thinking this in my head? HELP!!