Hi, you're right, stay away from negative people! The problem is, when you are bi-polar and have active symptoms, you don't know it.
Therefore, sometimes when people are telling you you are weird or are negative, sometimes, they are right. Just keep this in the back of your mind, after a while, you can start to recognise symptoms in yourself that are a tip-off to a depressive or manic episode.
And no, it's not your job to educate people about your condition. But if you care about someone, you should share what is going on with you. They probably, actually, care.
Best of luck
mia