Herx or drug reaction? How to tell the differance?

I have am on day four of Biaxin. Day on on 1 500mg tablet, Day 2 2 500mg tablet. Days three and four I dropped down back to one tablet because of the effects I was feeling. I do have some muscle twitching. My main problems are anxiety, GI, and feeling Spacey(drunk). Also, day two I had insomnia the whole night. Today, feelings of spaciness and crushing fatigue. I could go to sleep. I have twins and I need to be present for them. Will biaxin hit any pathogens in the CNS? I know it doesn't get into the tissues a lot, but will still do a little? I have another appointment with my LLMD and Wednesday and Im sure she is not going to be the happiest that Im not taking the full dose prescribed.