It all depends on what it means to be Jewish to you. If being Jewish is being a follower and believer of a religion - Jewish religion - then you're no longer Jewish (religiously speaking) because now you're an atheist. However, if you think that being Jewish is to belong to a racial group, the fact of being an atheist isn't going to change your race or ethnicity. If I convert to Tibetan Buddhism, I'll always belong to my own ethnic group. So what's the problem? Perhaps your friends have disowned and you feel alone and isolated (this problem exists in many religions, especially the evangelicals), then find new friends, you don't have any obligation towards some friends who don't respect your beliefs. Perhaps the problem is that you haven't been totally convinced by the philosophical and scientific explanations about the contradictions of religion, in this case go back to your old friends and try to live with the fantasy of religion. I wish I could be of more help.