Seeing White Smoke

A couple days ago my boyfriend and I went to the cemetery so I could practice driving. At one point we both got out of the car and started walking around looking at the graves. I had just bought a spirit box app and decided I would give it a try. Not really believing a phone app would really do anything anyways. At one point my boyfriend went one way and I went another. When we finally met back up we were both reading the info on a headstone when I looked up and saw a light cloud of white smoke next to my boyfriend and disappear towards the right row of graves. I followed the direction it went. Not sure why, did not see or find anything. I actually had to ask my boyfriend if he was smoking. (He doesn't even smoke). He said no so I told him what I seen. I don't think he believed me as he was trying to say it was a reflection of some sort. We looked around some more and went home. Well ever since that day I will randomly see this same thin white smoke by my boyfriend and then it disappears. The second time it happened in are bedroom and I found myself once again asking him if he was doing anything to cause smoke. He was laying on the bed watching tv so I could see he wasn't doing anything but I still had to ask. I never smell anything when I see this smoke. It never stays long either. I'm just curious as to what could be causing me to see this. Is it me? Is there something wrong with my eyes or brain? Should I be worried? Why do I only see this by my boyfriend and no where else?