Can you get altitude sickness at big bear?

About two years ago, I went snowboarding there with no problems, even spent the night once. Last year I went twice, once to snowboard, once to go horseback riding and got a migraine both times. Is it possible that it is altitude sickness? I didn't get it before, but it is possible to develop it over the years? Just wondering because my friends are planning a weekend up and I don't want to feel miserable the whole time.