And my concentration practice has increased finally. However, I noticed two things: I couldn't sleep as easily and when I do, my dreams are insanely vivid. Is this normal?
In my experience, this is very normal and the direct result of heavy concentration. If meditation is less heavily concentrated, this side-effect will not happen.
It has basically increased my anxiety now that I'm more aware of things going on. Is this an issue? Has anyone else had this experience? Any advice? It has actually freaked me out a bit, honestly. I got back into meditation to deal with anxiety, and now it seems to have made it more apparent.
Any meditation outside of just sitting at access concentration (which would diminish anxiety like the doctor said) is likely to shed light on the anxiety to get a better look at it, thus giving the feeling of more anxiety. In the short term, anxiety will likely worsen, in the long-term it will be alleviated. More important would be to ask yourself the question, what exactly IS anxiety in a direct non-conceptual way? It could be several years of meditation practice before you can really answer this.
EDIT: I would agree with fivebells that you should spend more time just sitting at access concentration and developing basic mindfulness before doing any insight practices. I spent 1.5-2 years doing this before starting insight practices.
It has actually freaked me out a bit
When dealing with your anxiety or any other psychological/psychiatric issues keep this in mind: Fear of madness IS madness.