If you are having anxiety problems, you should stay away from caffeine. I have an anxiety disorder and caffeine just triggers more anxiety. Also you may want to increase your Paxil (as that is a really low dose) or try another anxiety-specific med. Good luck!
Perhaps get to the root of why you need 3-5 cups of caffeine per day. If you're not able to make it through the day on your body's natural energy supplies, then perhaps there's an imbalance from lifestyle, diet, lack of exercise, or some other health issue. That same imbalance might be causing the anxiety.
I have a genetic pre-disposition to chemically-caused anxiety, but I cured it naturally. I had to take Paxil in college because I messed up my brain once when I took ecstasy. That through my whole delicate balance off and I had anxiety attacks for a few months.
I was able to cure myself by meditating for 30-60 minutes per day. Meditation releases serotonin naturally. But... Paxil is a good drug to take while you get to the point where you can cure it with your mind. Could take a couple years of meditation practice before you get there. Anti-depressants can be a good crutch. Then again, there are some cases where one should take them for longer. I'm not a doctor so don't take my advice without consulting a professional. Just relating my personal experience of what worked for me.
I agree with the other posters. Caffiene is a stimulant and increases your heart rate and blood pressure, which are anxiety symptoms and anxiety producing. You should switch to decaf or something else. Paxil 12.5, i'm assuming is CR and is a pretty low dose. I never prescibe Paxil CR because you see so much weight gain with paxil and it is non-generic and there are cheaper more effective options.