if it's that light headed feeling of 'whoa this is familiar' on a daily basis [almost] i'd see a doctor first.
our brain catches more than our eyes, and as we sleep our brain keeps working, once it figures something out, it tries to tell us through our dreams. a lot of the time our dreams are fun imaginations, but others they're prophetic or even psychic. without much detail beyond you have a dream then get deja vu, you're probably having prophetic dreams, your mind makes out what's going to happen. start keeping a dream diary, have it right by your bed so when you wake up, you can write everything down. since most of our dream is lost in less than 5 minutes, and there might be something important. keep in mind as i said not all dreams predict things, and not everything your dream says should be taken seriously, but it's a fun thing to do, and you should keep it in mind.
deja vu is different for each person. as a child i felt the rush of deja vu when i walked through one doorway in my grandparents house. it happened every time from age 7 to age 13, then it stopped. i don't think i've experienced any kind of deja vu since i was 16/17. if it happens a lot and you should look into it.